Argon is the third-most abundant gas in the Earth’s atmosphere, at 0.934% (9340 ppmv). Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning.
Argon is produced industrially by the fractional distillation of liquid air. a process that separates liquid nitrogen, which boils at 77.3 K, from argon, which boils at 87.3 K, and liquid oxygen, which boils at 90.2 K.
Protons and Neutrons in Argon
Argon is a chemical element with atomic number 18 which means there are 18 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 Argon are 36; 38; 40.
Main Isotopes of Argon
Nearly all of the argon in the Earth’s atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earth’s crust. Argon has 26 known isotopes, from 29Ar to 54Ar and 1 isomer (32mAr), of which three are stable (36Ar, 38Ar, and 40Ar). On the Earth, 40Ar makes up 99.6% of natural argon.
Argon-36 is composed of 18 protons, 18 neutrons, and 18 electrons.
Argon-38 is composed of 18 protons, 20 neutrons, and 18 electrons.
Argon-40 is composed of 18 protons, 22 neutrons, and 18 electrons. Almost all of the argon in the Earth’s atmosphere is the product of 40K decay, since 99.6% of Earth atmospheric argon is 40Ar.
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 Argon is 18. 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 Argon is [Ne] 3s2 3p6.
Possible oxidation states are 0.
Argon’s complete octet of electrons indicates full s and p subshells. This full valence shell makes argon very stable and extremely resistant to bonding with other elements. Before 1962, argon and the other noble gases were considered to be chemically inert and unable to form compounds; however, compounds of the heavier noble gases have since been synthesized.
Some Compound of Argon
Argon fluorohydride or argon hydrofluoride is an inorganic compound with the chemical formula HArF (also written ArHF).
|Number of protons
|Number of neutrons (typical isotopes)
|36; 38; 40
|Number of electrons
|[Ne] 3s2 3p6