Potassium is one of the alkali metals. All of the alkali metals have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge – a cation, which combines with anions to form salts. Naturally occurring potassium is composed of three isotopes, of which 40K is radioactive. Traces of 40K are found in all potassium, and it is the most common radioisotope in the human body.
Agricultural fertilizers consume 95% of global potassium chemical production, and about 90% of this potassium is supplied as KCl. Due to its high degree of reactivity, pure potassium is rarely used in its elemental /metallic form.
Potassium compounds can be extracted from the earth as it is found in many solids, soil and seawater.
Protons and Neutrons in Potassium
Potassium is a chemical element with atomic number 19 which means there are 19 protons in its nucleus. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10-19 coulombs.
The total number of neutrons in the nucleus of an atom is called the neutron number of the atom and is given the symbol N. Neutron number plus atomic number equals atomic mass number: N+Z=A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N – Z = A – 2Z.
For stable elements, there is usually a variety of stable isotopes. Isotopes are nuclides that have the same atomic number and are therefore the same element, but differ in the number of neutrons. Mass numbers of typical isotopes of Potassium are 39; 41.
Main Isotopes of Potassium
There are 25 known isotopes of potassium, three of which occur naturally: 39K (93.3%), 40K (0.0117%), and 41K (6.7%).
Potassium-39 is composed of 19 protons, 20 neutrons, and 19 electrons.
Potassium-40 is composed of 19 protons, 21 neutrons, and 19 electrons. Traces of K-40 are found in all potassium, and it is the most common radioisotope in the human body. K-40 is a radioactive isotope of potassium which has a very long half-life of 1.251×109 years and undergoes both types of beta decay.
- About 89.28% of the time (10.72% is by electron capture), it decays to calcium-40 with emission of a beta particle (β−, an electron) with a maximum energy of 1.33 MeV and an antineutrino, which is an antiparticle to the neutrino.
- Very rarely (0.001% of the time) it will decay to Ar-40 by emitting a positron (β+) and a neutrino.
Potassium-41 is composed of 19 protons, 22 neutrons, and 19 electrons.
Electrons and Electron Configuration
The number of electrons in an electrically-neutral atom is the same as the number of protons in the nucleus. Therefore, the number of electrons in neutral atom of Potassium is 19. Each electron is influenced by the electric fields produced by the positive nuclear charge and the other (Z – 1) negative electrons in the atom.
Since the number of electrons and their arrangement are responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements. 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.
Electron configuration of Potassium is [Ar] 4s1.
Possible oxidation states are +1.
Potassium is one of the alkali metals. All of the alkali metals have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge – a cation, which combines with anions to form salts. In general, potassium compounds are ionic and, owing to the high hydration energy of the K+ion, have excellent water solubility. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-colored flame.
Common Compound of Potassium
Common compound of potassium is potassium chloride, which is a metal halide salt composed of potassium and chlorine. KCl is used as a fertilizer, in medicine, in scientific applications, and in food processing, where it may be known as E number additive E508.
|Number of protons||19|
|Number of neutrons (typical isotopes)||39; 41|
|Number of electrons||19|
|Electron configuration||[Ar] 4s1|
Properties of other elements