Material Properties

Electrostatic Force – Formula – Coulomb’s Law

Forces between static electrically charged particles are governed by the Coulomb’s law. Coulomb’s Law can be used to calculate the force between charged particles (e.g. two protons). The electrostatic force is directly proportional to the electrical charges of the two particles and inversely proportional to the square of the distance between the particles. Coulomb’s Law is stated as the following equation.

Both, the Coulomb’s law and the magnetic force, are summarized in the Lorentz force law. Fundamentally, both magnetic and electric forces are manifestations of an exchange force involving the exchange of photons.

The photon, the quantum of electromagnetic radiation, is an elementary particle, which is the force carrier of the electromagnetic force. Photons are gauge bosons having no electric charge or rest mass and one unit of spin. Common to all photons is the speed of light, the universal constant of physics. In empty space, the photon moves at c (the speed of light – 299 792 458 metres per second).

The electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life. The chemical properties of atoms and molecules are determined by the number of protons, in fact, by number and arrangement of electrons. The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z. In fact, the forces of electric attraction and repulsion of electric charges are so dominant over the other three fundamental forces that they can be considered to be negligible as determiners of atomic and molecular structure.

Example: Electrostatic Force

Noteworthy, in a four liters of water there is about 2.1 x 10⁸C of total electron charge. Thus, if we place two bottles a meter apart, the electrons in one of the bottles repel those in the other bottle with a force of 4.1 x 10²⁶N. This tremendous force is comparable with the force than the planet Earth would weigh if weighed on another Earth. Ut, as was written, there are also positive (protons) and these charges tend to cancel each other out.

See also:

Electromagnetic Force

Weak Interaction – Weak Force

The weak interaction or weak force is one of the four fundamental forces and involves the exchange of the intermediate vector bosons, the W and the Z. Since these bosons are very massive (on the order of 80 GeV, the uncertainty principle dictates a range of about 10^-18 meters which is less than the diameter of a proton. As a result, the weak interaction takes place only at very small, sub-atomic distances.

The weak interaction responsible for some nuclear phenomena such as beta decay, which can be understood in terms of the weak force operating on the quarks within the neutron. One of two down quarks changes into an up quark by emitting a W^– boson (carries away a negative charge). The W^– boson then decays into a beta particle and an antineutrino. This process is equivalent to the process, in which a neutrino interacts with a neutron.

As can be seen from the figure, the weak interaction changes one flavor of quark into another. Note that, the Standard Model counts six flavours of quarks and six flavours of leptons. The weak interaction is the only process in which a quark can change to another quark, or a lepton to another lepton (flavor change). Neither the strong interaction nor electromagnetic permit flavour changing. This fact is crucial in many decays of nuclear particles. In the fusion process, which, for example, powers the Sun, two protons interact via the weak force to form a deuterium nucleus, which reacts further to generate helium. Without the weak interaction, the diproton would decay back into two hydrogen-1 unbound protons through proton emission. As a result, the sun would not burn without it since the weak interaction causes the transmutation p -> n.

Electroweak Interaction

Although weak force is considered one of the four fundamental forces, at high energy the weak force and electromagnetic force are unified as a single electroweak force. The unification energy is on the order of 100 GeV.  At low energies electromagnetic and weak interaction appear to be very different. Electroweak theory is very important for modern cosmology. In the history of the universe, during the quark epoch (shortly after the Big Bang) the unified force broke into the two separate forces as the universe cooled.

For contributions to the unification of the weak and electromagnetic interaction between elementary particles, Abdus Salam, Sheldon Glashow and Steven Weinberg were awarded the 1979 Nobel Prize in Physics.

See also:

Fundamental Interactions

Electroweak Interaction

Although weak force is considered one of the four fundamental forces, at high energy the weak force and electromagnetic force are unified as a single electroweak force. The unification energy is on the order of 100 GeV.  At low energies electromagnetic and weak interaction appear to be very different. Electroweak theory is very important for modern cosmology. In the history of the universe, during the quark epoch (shortly after the Big Bang) the unified force broke into the two separate forces as the universe cooled.

For contributions to the unification of the weak and electromagnetic interaction between elementary particles, Abdus Salam, Sheldon Glashow and Steven Weinberg were awarded the 1979 Nobel Prize in Physics.

Weak Interaction

The weak interaction or weak force is one of the four fundamental forces and involves the exchange of the intermediate vector bosons, the W and the Z. Since these bosons are very massive (on the order of 80 GeV, the uncertainty principle dictates a range of about 10^-18 meters which is less than the diameter of a proton. As a result, the weak interaction takes place only at very small, sub-atomic distances.

The weak interaction responsible for some nuclear phenomena such as beta decay, which can be understood in terms of the weak force operating on the quarks within the neutron. One of two down quarks changes into an up quark by emitting a W^– boson (carries away a negative charge). The W^– boson then decays into a beta particle and an antineutrino. This process is equivalent to the process, in which a neutrino interacts with a neutron.

Electromagnetic Interaction

The electromagnetic force is the force responsible for all electromagnetic processes. It acts between electrically charged particles. It is infinite-ranged force, much stronger than gravitational force, obeys the inverse square law, but neither electricity nor magnetism adds up in the way that gravitational force does. Since there are positive and negative charges (poles), these charges tend to cancel each other out. Electromagnetism includes the electrostatic force acting between charged particles at rest, and the combined effect of electric and magnetic forces acting between charged particles moving relative to each other.

The photon, the quantum of electromagnetic radiation, is an elementary particle, which is the force carrier of the electromagnetic force. Photons are gauge bosons having no electric charge or rest mass and one unit of spin. Common to all photons is the speed of light, the universal constant of physics. In empty space, the photon moves at c (the speed of light – 299 792 458 metres per second).

See also:

Fundamental Interactions

Strong Interaction – Strong Force

The strong interaction or strong force is one of the four fundamental forces and involves the exchange of the vector gauge bosons known as gluons. In general, the strong interaction is very complicated interaction, because it significantly varies with distance. The strong nuclear force holds most ordinary matter together because it confines quarks into hadron particles such as the proton and neutron. Moreover, the strong force is the force which can hold a nucleus together against the enormous forces of repulsion (electromagnetic force) of the protons is strong indeed. From this point of view, we have to distinguish between:

• Fundamental Strong Force. The fundamental strong force, or the strong force, is a very short range (less than about 0.8 fm, the radius of a nucleon) force, that acts directly between quarks. This force holds quarks together to form protons, neutrons, and other hadron particles. The strong interaction is mediated by the exchange of massless particles called gluons that act between quarks, antiquarks, and other gluons.
• Residual Strong Force. The residual strong force, also known as the nuclear force, is a very short range (about 1 to 3 fm) force, which acts to hold neutrons and protons together in nuclei. In nuclei, this force acts against the enormous repulsive electromagnetic force of the protons. The term residual is associated with the fact, it is the residuum of the fundamental strong interaction between the quarks that make up the protons and neutrons. The residual strong force acts indirectly through the virtual π and ρ mesons, which transmit the force between nucleons that holds the nucleus together.

In strong interactions the quarks exchange gluons, the carriers of the strong force. Gluons carry the color charge of the strong nuclear force. Color charge is analogous to electromagnetic charge, but quarks carry three types of color charge (red, green, blue) and antiquarks carry three types of anticolor (antired, antigreen, antiblue). Gluons may be thought of as carrying both color and anticolor.

Most of the mass of a common proton or neutron is the result of the strong force field energy. The individual quarks provide only about 1% of the mass of a proton. Noteworthy, because most of yourthermodynamics/thermodynamic-properties/what-is-mass-and-weight/”> mass is due to the protons and neutrons in your body, your mass (and therefore your weight on a bathroom scale) comes primarily from the gluons that bind the constituent quarks together, rather than from the quarks themselves. Mass is primarily a measure of the energies of the quark motion and the quark-binding fields.

Range of Strong Force

As was written, the strong interaction is very complicated interaction, because it significantly varies with distance. At distances comparable to the diameter of a proton, the strong force is approximately 100 times as strong as electromagnetic force. At smaller distances, however, the strong force between quarks becomes weaker, and the quarks begin to behave like independent particles. In particle physics, this effect is known as asymptotic freedom.

As a result, the strong force can leaks out of individual nucleons (as the residual strong force) to influence the adjacent particle. On the other hand, the strong force cannot reach outside the nucleus. This is due to color confinement, which implies that the strong force acts only between pairs of quarks. Simply, color charged particles (such as quarks and gluons) cannot be isolated (below Hagedorn temperature) and therefore in collections of bound quarks (i.e., hadrons), the net color-charge of the quarks essentially cancels out, resulting in a limit of the action of the forces.

Strength of Strong Force

It is the strongest of the four fundamental forces, but as was written, it significantly varies with distance. At the scale of quarks, the strong force is approximately 100 times as strong as electromagnetic force, a million times as strong as the weak interaction, and 10⁴³ times as strong as gravitation.

What are Gluons – Mass of Quark

The mass of the neutron is 939.565 MeV/c², whereas the mass of the three quarks is only about 10 MeV/c² (only about 1% of the mass-energy of the neutron). Like the proton, most of mass (energy) of the neutron is in the form of the strong nuclear force energy (gluons). The quarks of the neutron are held together by gluons, the exchange particles for the strong nuclear force. Gluons carry the color charge of the strong nuclear force.

Therefore, we have to distinguish between current quark mass (also called the mass of the ‘naked’ quarks) and constituent quark mass. Current quark mass refers to the mass of a quark by itself, while constituent quark mass refers to the current quark mass plus the mass of the gluon particle field surrounding the quark.

Noteworthy, because most of your mass is due to the protons and neutrons in your body, your mass (and therefore your weight on a bathroom scale) comes primarily from the gluons that bind the constituent quarks together, rather than from the quarks themselves. Mass is primarily a measure of the energies of the quark motion and the quark-binding fields any real object. It must be noted, gluons are inherently massless, they possess energy.

Particles in Strong Interaction

In general, particles that do participate in strong interactions are called hadrons: protons and neutrons are hadrons. The hadrons are further sub-divided into baryons and mesons, according to the number of quarks they contain. Protons and neutrons each contain three quarks; they belong to the family of particles called the baryons. Other baryons are the lambda, sigma, xi, and omega particles. On the other hand mesons bosons and they are composed of two quarks: a quark and an antiquark. Besides charge and spin (1/2 for the baryons), two other quantum numbers are assigned to these particles: baryon number (B) and strangeness (S). Baryons have a baryon number, B, of 1, while their antiparticles, called antibaryons, have a baryon number of −1. A nucleus of deuterium (deuteron), for example, contains one proton and one neutron (each with a baryon number of 1) and has a baryon number of 2. Since baryons make up most of the mass of ordinary atoms, the everyday matter is often referred to as baryonic matter.

The conservation of baryon number is an important rule for interactions and decays of baryons. No known interactions violate conservation of baryon number.

Nuclear Force – Residual Strong Force

The residual strong force, also known as the nuclear force, is a very short range (about 1 to 3 fm) force, which acts to hold neutrons and protons together in nuclei. In nuclei, this force acts against the enormous repulsive electromagnetic force of the protons. It acts equally only between pairs of neutrons, pairs of protons, or a neutron and a proton. The term residual is associated with the fact, it is the residuum of the fundamental strong interaction between the quarks that make up the protons and neutrons. The residual strong force acts indirectly through the virtual π and ρ mesons, which transmit the force between nucleons that holds the nucleus together.

As was written, hadrons appear nearly without color charge, and the fundamental strong force is therefore nearly absent between those hadrons except that the cancellation is not quite perfect. The fundamental strong force can leaks out of individual nucleons (as the residual strong force) to influence the adjacent particle. As for the fundamental strong force, the residual force does diminish rapidly with distance, and is thus very short-range. Therefore, neither the residual strong force cannot reach outside the nucleus. This is due to color confinement, which implies that the strong force acts only between pairs of quarks. Simply, color charged particles (such as quarks and gluons) cannot be isolated (below Hagedorn temperature) and therefore in collections of bound quarks (i.e., hadrons), the net color-charge of the quarks essentially cancels out, resulting in a limit of the action of the forces.

Notwithstanding they have identical origin, the residual strong force is much weaker than the fundamental strong force. It is very much like the electromagnetic forces between neutral atoms (van der Waals forces), which form molecules and are much weaker than the electromagnetic forces that hold electrons in association with the nucleus, forming the atoms.

Atomic nuclei consist of protons and neutrons, which attract each other through the nuclear force, while protons repel each other via the electromagnetic force due to their positive charge. These two forces compete, leading to various stability of nuclei. There are only certain combinations of neutrons and protons, which forms stable nuclei. Neutrons stabilize the nucleus, because they attract each other and protons , which helps offset the electrical repulsion between protons. As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus. If there are too many (neutrons also obey the Pauli exclusion principle) or too few neutrons for a given number of protons, the resulting nucleus is not stable and it undergoes radioactive decay. Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, or electron capture. Many other rare types of decay, such as spontaneous fission or neutron emission are known.

See also: Liquid Drop Model

See also:

Fundamental Interactions

Characteristics of Strong Interaction

The strong interaction or strong force is one of the four fundamental forces and involves the exchange of the vector gauge bosons known as gluons. In general, the strong interaction is very complicated interaction, because it significantly varies with distance.

In strong interactions the quarks exchange gluons, the carriers of the strong force. Gluons carry the color charge of the strong nuclear force. Color charge is analogous to electromagnetic charge, but quarks carry three types of color charge (red, green, blue) and antiquarks carry three types of anticolor (antired, antigreen, antiblue). Gluons may be thought of as carrying both color and anticolor.

Most of the mass of a common proton or neutron is the result of the strong force field energy. The individual quarks provide only about 1% of the mass of a proton. Noteworthy, because most of yourthermodynamics/thermodynamic-properties/what-is-mass-and-weight/”> mass is due to the protons and neutrons in your body, your mass (and therefore your weight on a bathroom scale) comes primarily from the gluons that bind the constituent quarks together, rather than from the quarks themselves. Mass is primarily a measure of the energies of the quark motion and the quark-binding fields.

Range of Strong Force

As was written, the strong interaction is very complicated interaction, because it significantly varies with distance. At distances comparable to the diameter of a proton, the strong force is approximately 100 times as strong as electromagnetic force. At smaller distances, however, the strong force between quarks becomes weaker, and the quarks begin to behave like independent particles. In particle physics, this effect is known as asymptotic freedom.

As a result, the strong force can leaks out of individual nucleons (as the residual strong force) to influence the adjacent particle. On the other hand, the strong force cannot reach outside the nucleus. This is due to color confinement, which implies that the strong force acts only between pairs of quarks. Simply, color charged particles (such as quarks and gluons) cannot be isolated (below Hagedorn temperature) and therefore in collections of bound quarks (i.e., hadrons), the net color-charge of the quarks essentially cancels out, resulting in a limit of the action of the forces.

Strength of Strong Force

It is the strongest of the four fundamental forces, but as was written, it significantly varies with distance. At the scale of quarks, the strong force is approximately 100 times as strong as electromagnetic force, a million times as strong as the weak interaction, and 10⁴³ times as strong as gravitation.

Particles in Strong Interaction

In general, particles that do participate in strong interactions are called hadrons: protons and neutrons are hadrons. The hadrons are further sub-divided into baryons and mesons, according to the number of quarks they contain. Protons and neutrons each contain three quarks; they belong to the family of particles called the baryons. Other baryons are the lambda, sigma, xi, and omega particles. On the other hand mesons bosons and they are composed of two quarks: a quark and an antiquark. Besides charge and spin (1/2 for the baryons), two other quantum numbers are assigned to these particles: baryon number (B) and strangeness (S). Baryons have a baryon number, B, of 1, while their antiparticles, called antibaryons, have a baryon number of −1. A nucleus of deuterium (deuteron), for example, contains one proton and one neutron (each with a baryon number of 1) and has a baryon number of 2. Since baryons make up most of the mass of ordinary atoms, the everyday matter is often referred to as baryonic matter.

The conservation of baryon number is an important rule for interactions and decays of baryons. No known interactions violate conservation of baryon number.

See also:

Strong Interactions

What are Gluons

In strong interactions the quarks exchange gluons, the carriers of the strong force. Gluons, the vector gauge bosons, carry the color charge of the strong nuclear force. Color charge is analogous to electromagnetic charge, but quarks carry three types of color charge (red, green, blue) and antiquarks carry three types of anticolor (antired, antigreen, antiblue). Gluons may be thought of as carrying both color and anticolor.  The strong nuclear force holds most ordinary matter together because it confines quarks into hadron particles such as the proton and neutron. Moreover, the strong force is the force which can hold a nucleus together against the enormous forces of repulsion (electromagnetic force) of the protons is strong indeed.

The strong interaction is very complicated interaction, because it significantly varies with distance. At distances comparable to the diameter of a proton, the strong force is approximately 100 times as strong as electromagnetic force. At smaller distances, however, the strong force between quarks becomes weaker, and the quarks begin to behave like independent particles. In particle physics, this effect is known as asymptotic freedom.

As a result, the strong force can leaks out of individual nucleons (as the residual strong force) to influence the adjacent particle. On the other hand, the strong force cannot reach outside the nucleus. This is due to color confinement, which implies that the strong force acts only between pairs of quarks. Simply, color charged particles (such as quarks and gluons) cannot be isolated (below Hagedorn temperature) and therefore in collections of bound quarks (i.e., hadrons), the net color-charge of the quarks essentially cancels out, resulting in a limit of the action of the forces.

Gluons and Mass of Quarks

The mass of the neutron is 939.565 MeV/c², whereas the mass of the three quarks is only about 10 MeV/c² (only about 1% of the mass-energy of the neutron). Like the proton, most of mass (energy) of the neutron is in the form of the strong nuclear force energy (gluons). The quarks of the neutron are held together by gluons, the exchange particles for the strong nuclear force. Gluons carry the color charge of the strong nuclear force.

Therefore, we have to distinguish between current quark mass (also called the mass of the ‘naked’ quarks) and constituent quark mass. Current quark mass refers to the mass of a quark by itself, while constituent quark mass refers to the current quark mass plus the mass of the gluon particle field surrounding the quark.

Noteworthy, because most of your mass is due to the protons and neutrons in your body, your mass (and therefore your weight on a bathroom scale) comes primarily from the gluons that bind the constituent quarks together, rather than from the quarks themselves. Mass is primarily a measure of the energies of the quark motion and the quark-binding fields any real object. It must be noted, gluons are inherently massless, they possess energy.

See also:

Strong Interactions

Fundamental Strong Force

The strong interaction or strong force is one of the four fundamental forces and involves the exchange of the vector gauge bosons known as gluons. In general, the strong interaction is very complicated interaction, because it significantly varies with distance. The strong nuclear force holds most ordinary matter together because it confines quarks into hadron particles such as the proton and neutron. Moreover, the strong force is the force which can hold a nucleus together against the enormous forces of repulsion (electromagnetic force) of the protons is strong indeed. From this point of view, we have to distinguish between:

• Fundamental Strong Force. The fundamental strong force, or the strong force, is a very short range (less than about 0.8 fm, the radius of a nucleon) force, that acts directly between quarks. This force holds quarks together to form protons, neutrons, and other hadron particles. The strong interaction is mediated by the exchange of massless particles called gluons that act between quarks, antiquarks, and other gluons.
• Residual Strong Force. The residual strong force, also known as the nuclear force, is a very short range (about 1 to 3 fm) force, which acts to hold neutrons and protons together in nuclei. In nuclei, this force acts against the enormous repulsive electromagnetic force of the protons. The term residual is associated with the fact, it is the residuum of the fundamental strong interaction between the quarks that make up the protons and neutrons. The residual strong force acts indirectly through the virtual π and ρ mesons, which transmit the force between nucleons that holds the nucleus together.

In strong interactions the quarks exchange gluons, the carriers of the strong force. Gluons carry the color charge of the strong nuclear force. Color charge is analogous to electromagnetic charge, but quarks carry three types of color charge (red, green, blue) and antiquarks carry three types of anticolor (antired, antigreen, antiblue). Gluons may be thought of as carrying both color and anticolor.

Most of the mass of a common proton or neutron is the result of the strong force field energy. The individual quarks provide only about 1% of the mass of a proton. Noteworthy, because most of yourthermodynamics/thermodynamic-properties/what-is-mass-and-weight/”> mass is due to the protons and neutrons in your body, your mass (and therefore your weight on a bathroom scale) comes primarily from the gluons that bind the constituent quarks together, rather than from the quarks themselves. Mass is primarily a measure of the energies of the quark motion and the quark-binding fields.

Range of Strong Force

As was written, the strong interaction is very complicated interaction, because it significantly varies with distance. At distances comparable to the diameter of a proton, the strong force is approximately 100 times as strong as electromagnetic force. At smaller distances, however, the strong force between quarks becomes weaker, and the quarks begin to behave like independent particles. In particle physics, this effect is known as asymptotic freedom.

As a result, the strong force can leaks out of individual nucleons (as the residual strong force) to influence the adjacent particle. On the other hand, the strong force cannot reach outside the nucleus. This is due to color confinement, which implies that the strong force acts only between pairs of quarks. Simply, color charged particles (such as quarks and gluons) cannot be isolated (below Hagedorn temperature) and therefore in collections of bound quarks (i.e., hadrons), the net color-charge of the quarks essentially cancels out, resulting in a limit of the action of the forces.

Strength of Strong Force

It is the strongest of the four fundamental forces, but as was written, it significantly varies with distance. At the scale of quarks, the strong force is approximately 100 times as strong as electromagnetic force, a million times as strong as the weak interaction, and 10⁴³ times as strong as gravitation.

See also:

Strong Interactions

Nuclear Force – Residual Strong Force

The strong interaction or strong force is one of the four fundamental forces and involves the exchange of the vector gauge bosons known as gluons. In general, the strong interaction is very complicated interaction, because it significantly varies with distance. The strong nuclear force holds most ordinary matter together because it confines quarks into hadron particles such as the proton and neutron. Moreover, the strong force is the force which can hold a nucleus together against the enormous forces of repulsion (electromagnetic force) of the protons is strong indeed. From this point of view, we have to distinguish between:

• Fundamental Strong Force. The fundamental strong force, or the strong force, is a very short range (less than about 0.8 fm, the radius of a nucleon) force, that acts directly between quarks. This force holds quarks together to form protons, neutrons, and other hadron particles. The strong interaction is mediated by the exchange of massless particles called gluons that act between quarks, antiquarks, and other gluons.
• Residual Strong Force. The residual strong force, also known as the nuclear force, is a very short range (about 1 to 3 fm) force, which acts to hold neutrons and protons together in nuclei. In nuclei, this force acts against the enormous repulsive electromagnetic force of th
  e protons. The term residual is associated with the fact, it is the residuum of the fundamental strong interaction between the quarks that make up the protons and neutrons. The residual strong force acts indirectly through the virtual π and ρ mesons, which transmit the force between nucleons that holds the nucleus together.

In strong interactions the quarks exchange gluons, the carriers of the strong force. Gluons carry the color charge of the strong nuclear force. Color charge is analogous to electromagnetic charge, but quarks carry three types of color charge (red, green, blue) and antiquarks carry three types of anticolor (antired, antigreen, antiblue). Gluons may be thought of as carrying both color and anticolor.

Most of the mass of a common proton or neutron is the result of the strong force field energy. The individual quarks provide only about 1% of the mass of a proton. Noteworthy, because most of yourthermodynamics/thermodynamic-properties/what-is-mass-and-weight/”> mass is due to the protons and neutrons in your body, your mass (and therefore your weight on a bathroom scale) comes primarily from the gluons that bind the constituent quarks together, rather than from the quarks themselves. Mass is primarily a measure of the energies of the quark motion and the quark-binding fields.

Characteristics of Nuclear Force

The residual strong force, also known as the nuclear force, is a very short range (about 1 to 3 fm) force, which acts to hold neutrons and protons together in nuclei. In nuclei, this force acts against the enormous repulsive electromagnetic force of the protons. It acts equally only between pairs of neutrons, pairs of protons, or a neutron and a proton. The term residual is associated with the fact, it is the residuum of the fundamental strong interaction between the quarks that make up the protons and neutrons. The residual strong force acts indirectly through the virtual π and ρ mesons, which transmit the force between nucleons that holds the nucleus together.

As was written, hadrons appear nearly without color charge, and the fundamental strong force is therefore nearly absent between those hadrons except that the cancellation is not quite perfect. The fundamental strong force can leaks out of individual nucleons (as the residual strong force) to influence the adjacent particle. As for the fundamental strong force, the residual force does diminish rapidly with distance, and is thus very short-range. Therefore, neither the residual strong force cannot reach outside the nucleus. This is due to color confinement, which implies that the strong force acts only between pairs of quarks. Simply, color charged particles (such as quarks and gluons) cannot be isolated (below Hagedorn temperature) and therefore in collections of bound quarks (i.e., hadrons), the net color-charge of the quarks essentially cancels out, resulting in a limit of the action of the forces.

Notwithstanding they have identical origin, the residual strong force is much weaker than the fundamental strong force. It is very much like the electromagnetic forces between neutral atoms (van der Waals forces), which form molecules and are much weaker than the electromagnetic forces that hold electrons in association with the nucleus, forming the atoms.

Atomic nuclei consist of protons and neutrons, which attract each other through the nuclear force, while protons repel each other via the electromagnetic force due to their positive charge. These two forces compete, leading to various stability of nuclei. There are only certain combinations of neutrons and protons, which forms stable nuclei. Neutrons stabilize the nucleus, because they attract each other and protons , which helps offset the electrical repulsion between protons. As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus. If there are too many (neutrons also obey the Pauli exclusion principle) or too few neutrons for a given number of protons, the resulting nucleus is not stable and it undergoes radioactive decay. Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, or electron capture. Many other rare types of decay, such as spontaneous fission or neutron emission are known.

See also: Liquid Drop Model

See also:

Strong Interactions

What is Atom

The physical world is composed of combinations of various subatomic or fundamental particles. These are the smallest building blocks of matter. All matter except dark matter is made of molecules, which are themselves made of atoms. The atoms are the smallest constituents of ordinary matter, which can be divided without the release of electrically charged particles. The atoms consist of two parts. An atomic nucleus and an electron cloud. The electrons are spinning around the atomic nucleus. The nucleus itself is generally made of protons and neutrons but even these are composite objects. Inside the protons and neutrons, we find the quarks.

The science, which deals with atoms is called atomic physics. Note that, atomic and nuclear physics are not the same. The term atomic physics is often associated with nuclear power, due to the synonymous use of atomic and nuclear in standard English. However, physicists distinguish between atomic and nuclear physics. The atomic physics deals with the atom as a system consisting of a nucleus and electrons. The nuclear physics deals with the nucleus as a system consisting of a nucleons (protons and neutrons). Main difference is in the scale. While the term atomic deals with 1Å = 10^-10m, where Å is an ångström (according to Anders Jonas Ångström), the  term nuclear deals with  1femtometre = 1fermi = 10^-15m.

Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change. This includes ions as well as neutral atoms and, unless otherwise stated, for the purposes of this discussion it should be assumed that the term atom includes ions. Atomic physics also help to understand the physics of molecules, but there is also molecular physics, which describes physical properties of molecules.

See also: Atomic and Nuclear Physics

Properties of Atoms

Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. The chemical properties of the atom are determined by the number of protons, in fact, by number and arrangement of electrons. The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z.

Atomic Number – Chemical Properties

The total number of protons in the nucleus of an atom is called the atomic number (or the proton number) of the atom and is given the symbol Z. The number of electrons in an electrically-neutral atom is the same as the number of protons in the nucleus. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10^-19coulombs. Each electron is influenced by the electric fields produced by the positive nuclear charge and the other (Z – 1) negative electrons in the atom.

It is the Pauli exclusion principle that requires the electrons in an atom to occupy different energy levels instead of them all condensing in the ground state. The ordering of the electrons in the ground state of multielectron atoms, starts with the lowest energy state (ground state) and moves progressively from there up the energy scale until each of the atom’s electrons has been assigned a unique set of quantum numbers. This fact has key implications for the building up of the periodic table of elements.

Mass Number – Mass of Atom

Since electrons are almost massless (in comparision to the nucleons), the total number of protons and neutrons in the nucleus of an atom determines the atomic mass. The total number of protons and neutrons in the nucleus of an atom is called the atomic mass number (or the mass number) of the atom and is given the symbol A. The mass number is different for each different isotope of a chemical element. The mass number is written either after the element name or as a superscript to the left of an element’s symbol. For example, the most common isotope of carbon is carbon-12, or ¹²C.

The unit of measure for mass is the atomic mass unit (amu). One atomic mass unit is equal to 1.66 x 10^-24 grams.

Besides the thermodynamics/thermodynamic-properties/what-is-mass-and-weight/standard-kilogram/”>standard kilogram, it is a second mass standard. It is the carbon-12 atom, which, by international agreement, has been assigned a mass of 12 atomic mass units (u). The relation between the two units is

One atomic mass unit is equal:

1u = 1.66 x 10^-24 grams.

One unified atomic mass unit is approximately the mass of one nucleon (either a single proton or neutron) and is numerically equivalent to 1 g/mol.

For ¹²C the atomic mass is exactly 12u, since the atomic mass unit is defined from it. For other isotopes, the isotopic mass usually differs and is usually within 0.1 u of the mass number. For example, ⁶³Cu (29 protons and 34 neutrons) has a mass number of 63 and an isotopic mass in its nuclear ground state is 62.91367 u.

There are two reasons for the difference between mass number and isotopic mass, known as the mass defect:

1. The neutron is slightly heavier than the proton. This increases the mass of nuclei with more neutrons than protons relative to the atomic mass unit scale based on ¹²C with equal numbers of protons and neutrons.
2. The nuclear binding energy varies between nuclei. A nucleus with greater binding energy has a lower total energy, and therefore a lower mass according to Einstein’s mass-energy equivalence relation E = mc². For ⁶³Cu the atomic mass is less than 63 so this must be the dominant factor.

Ionization Energy of Atoms

Ionization energy, also called ionization potential, is the energy necessary to remove an electron from the neutral atom.

X + energy → X⁺ + e⁻

where X is any atom or molecule capable of being ionized, X⁺ is that atom or molecule with an electron removed (positive ion), and e⁻ is the removed electron.

There is an ionization energy for each successive electron removed. The electrons that circle the nucleus move in fairly well-defined orbits. Some of these electrons are more tightly bound in the atom than others. For example, only 7.38 eV is required to remove the outermost electron from a lead atom, while 88,000 eV is required to remove the innermost electron.

• Ionization energy is lowest for the alkali metals which have a single electron outside a closed shell.
• Ionization energy increases across a row on the periodic maximum for the noble gases which have closed shells.

For example, sodium requires only 496 kJ/mol or 5.14 eV/atom to ionize it. On the other hand neon, the noble gas, immediately preceding it in the periodic table, requires 2081 kJ/mol or 21.56 eV/atom.

The ionization energy associated with removal of the first electron is most commonly used. The nth ionization energy refers to the amount of energy required to remove an electron from the species with a charge of (n-1).

1st ionization energy

X → X⁺ + e⁻

2nd ionization energy

X⁺ → X²⁺ + e⁻

3rd ionization energy

X²⁺ → X³⁺ + e⁻

For example, only 7.38 eV is required to remove the outermost electron from a lead atom, while 88,000 eV is required to remove the innermost electron.

Volume of Atom

The volume of an atom is about 15 orders of magnitude larger than the volume of a nucleus. For uranium atom, the Van der Waals radius is about 186 pm = 1.86 ×10⁻¹⁰m. The Van der Waals radius, r_w, of an atom is the radius of an imaginary hard sphere representing the distance of closest approach for another atom.  Assuming spherical shape, the uranium atom have volume of about  26.9 ×10⁻³⁰ m³. But this “huge” space is occupied primarily by electrons, because the nucleusoccupies only about 1721×10⁻⁴⁵ m³ of space. These electrons together weigh only a fraction (let say 0.05%) of entire atom.

It may seem, that the space and in fact the matter is empty, but it is not. Due to the quantum nature of electrons, the electrons are not point particles, they are smeared out over the whole atom. The classical description cannot be used to describe things on the atomic scale. On the atomic scale, physicists have found that quantum mechanics describes things very well on that scale. Particle locations in quantum mechanics are not at an exact position, they are described by a probability density function. Therefore the space in an atom (between electrons and an atomic nucleus) is not empty, but it is filled by a probability density function of electrons (usually known as  “electron cloud“).

Antiatom

Antimatter is a term referring to material that would be made up of “antiatoms” in which antiprotons and antineutrons would form the nucleus around which positrons (antielectrons) would move. The term is also used for antiparticles in general.

Antimatter particles bind with one another to form antimatter, just as ordinary particles bind to form normal matter. For example, a positron and an antiproton can form an antihydrogen atom. Physical principles indicate that complex antimatter atomic nuclei are possible, as well as anti-atoms corresponding to the known chemical elements.

Our visible Universe is almost entirely composed of matter, and very little antimatter has existed since the Big Bang. This problem is known as the baryon asymmetry. This asymmetry of matter and antimatter in the visible universe is one of the great unsolved problems in physics.

In special theory of relativity certain types of matter may be created or destroyed, but in all of these processes, the mass and energy associated with such matter remains unchanged in quantity. As a result of the conservation of lepton and baryon numbers,  antimatter (antiparticles) can be created out of energy, but only if a particle counterpart for every antiparticle is created as well.

See also: Matter – Antimatter Creation and Annihilation

See also:

Atomic Physics

Chemical Properties of Atoms

Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. The chemical properties of the atom are determined by the number of protons, in fact, by number and arrangement of electrons. The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z.

The total number of protons in the nucleus of an atom is called the atomic number (or the proton number) of the atom and is given the symbol Z. The number of electrons in an electrically-neutral atom is the same as the number of protons in the nucleus. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10^-19coulombs. Each electron is influenced by the electric fields produced by the positive nuclear charge and the other (Z – 1) negative electrons in the atom.

It is the Pauli exclusion principle that requires the electrons in an atom to occupy different energy levels instead of them all condensing in the ground state. The ordering of the electrons in the ground state of multielectron atoms, starts with the lowest energy state (ground state) and moves progressively from there up the energy scale until each of the atom’s electrons has been assigned a unique set of quantum numbers. This fact has key implications for the building up of the periodic table of elements.

Electron Affinity

In chemistry and atomic physics, the electron affinity of an atom or molecule is defined as:

the change in energy (in kJ/mole) of a neutral atom or molecule (in the gaseous phase) when an electron is added to the atom to form a negative ion.

X + e^– → X^– + energy        Affinity = – ∆H

In other words, it can be expressed as the neutral atom’s likelihood of gaining an electron. Note that, ionization energies measure the tendency of a neutral atom to resist the loss of electrons. Electron affinities are more difficult to measure than ionization energies.

A fluorine atom in the gas phase, for example, gives off energy when it gains an electron to form a fluoride ion.

F + e^– → F^–        – ∆H = Affinity = 328 kJ/mol

To use electron affinities properly, it is essential to keep track of sign. When an electron is added to a neutral atom, energy is released. This affinity is known as the first electron affinity and these energies are negative. By convention, the negative sign shows a release of energy. However, more energy is required to add an electron to a negative ion which overwhelms any the release of energy from the electron attachment process. This affinity is known as the second electron affinity and these energies are positive.

Affinities of Non metals vs. Affinities of Metals

• Metals: Metals like to lose valence electrons to form cations to have a fully stable shell. The electron affinity of metals is lower than that of nonmetals. Mercury most weakly attracts an extra electron.
• Nonmetals: Generally, nonmetals have more positive electron affinity than metals. Nonmetals like to gain electrons to form anions to have a fully stable electron shell. Chlorine most strongly attracts extra electrons. The electron affinities of the noble gases have not been conclusively measured, so they may or may not have slightly negative values.

Electronegativity

Electronegativity, symbol χ, is a chemical property that describes the tendency of an atom to attract electrons towards this atom. For this purposes, a dimensionless quantity the Pauling scale, symbol χ, is the most commonly used.

The electronegativity of fluorine is:

χ = 4.0

In general, an atom’s electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity number, the more an element or compound attracts electrons towards it.

The most electronegative atom, fluorine, is assigned a value of 4.0, and values range down to cesium and francium which are the least electronegative at 0.7.

Ionization Energy

Ionization energy, also called ionization potential, is the energy necessary to remove an electron from the neutral atom.

X + energy → X⁺ + e⁻

where X is any atom or molecule capable of being ionized, X⁺ is that atom or molecule with an electron removed (positive ion), and e⁻ is the removed electron.

A nitrogen atom, for example, requires the following ionization energy to remove the outermost electron.

N + IE → N⁺ + e⁻        IE = 14.5 eV

The ionization energy associated with removal of the first electron is most commonly used. The nth ionization energy refers to the amount of energy required to remove an electron from the species with a charge of (n-1).

1st ionization energy

X → X⁺ + e⁻

2nd ionization energy

X⁺ → X²⁺ + e⁻

3rd ionization energy

X²⁺ → X³⁺ + e⁻

Ionization Energy for different Elements

There is an ionization energy for each successive electron removed. The electrons that circle the nucleus move in fairly well-defined orbits. Some of these electrons are more tightly bound in the atom than others. For example, only 7.38 eV is required to remove the outermost electron from a lead atom, while 88,000 eV is required to remove the innermost electron. Helps to understand reactivity of elements (especially metals, which lose electrons).

In general, the ionization energy increases moving up a group and moving left to right across a period. Moreover:

• Ionization energy is lowest for the alkali metals which have a single electron outside a closed shell.
• Ionization energy increases across a row on the periodic maximum for the noble gases which have closed shells

For example, sodium requires only 496 kJ/mol or 5.14 eV/atom to ionize it. On the other hand neon, the noble gas, immediately preceding it in the periodic table, requires 2081 kJ/mol or 21.56 eV/atom.

See also:

Atom