How many valence electrons are there in AR?

Argon, a chemical element with the symbol Ar and atomic number 18, is a colorless, odorless, tasteless, non-flammable, nontoxic inert gas. It is the third most abundant gas on the earth's atmosphere (abundance is more than twice water vapor).

Its main isotopes are 40Ar (99.6%), 36Ar (0.34%) and 38Ar (0.06%) found on the earth's surface. Although it is a noble gas, it can form various compounds under various standard extreme conditions. Argon fluorohydride (HArF), tungsten pentacarbonyl [W(CO)5Ar], and argon hydride [Ar(H2)2] are some common compounds of argon.

You are here to know valence electrons and valency of argon, aren’t you? But before that let's have some ideas about what these two terms are:

Difference Between Valence Electrons and Valency

Valence electrons are the total number of electrons present in the outermost shell of an atom (i.e. in outermost orbital). The valence electrons for a neutral atom is always definite, it cannot be varied (more or less) in any condition for a particular atom and may or may not be equal to its valency.

Valency is defined as the total number of electrons an atom can lose, gain, or share at the time of bond formation to get a stable electronic configuration i.e. to complete an octet. The valency of an atom can be variable in different compounds or chemical reactions due to the different bonding circumstances. Most of the time valency varies/changes due to change in oxidation and reduction states.

Argon (Ar) Valence Electrons

There are four simple steps to find out the valence electrons for argon atom which are:

Step 1: Find the Atomic Number

To find out the atomic number of argon, we can use the periodic table. With the help of the periodic table, we can easily see that the atomic number of argon is 18. As its atomic number is 18, it has 18 protons, and for neutral argon, the number of protons is always equal to the number of electrons i.e. has 18 electrons in its nucleus.

Step 2: Write Electron Configuration

Electron configuration is the arrangement of electrons on the orbitals. The argon atom has a total of 18 electrons so, we have to put 18 electrons in orbitals. The electrons will be placed in orbital according to this energy levels: [1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f]. Now,

Argon electron configuration Ar (18) = 1s22s²2p⁶3s²3p⁶ (complete configuration)

= [Ne]3s²3p⁶ (condensed configuration).

Step3: Determine Valence Shell

As we know, the valence shell of an atom can be found from the highest number of principle quantum numbers which is expressed in the term of n, and in [Ne]3s²3p⁶, the highest value of n is 3 so that the valence shell of Ar is 3s²3p⁶.

Step 4: Find Valence Electrons

The total number of electrons present in the valence shell of an atom is called valence electrons, and there are eight electrons present in the valence shell of argon (3s²3p⁶). Thus, argon has eight valence electrons.

Valency of Argon (Ar)

There are many different ways to find out the valency of an atom which reflects the ability of an atom to bond with other atoms. Valence describes how easily an atom or a free radical can combine with other chemical species. The valency of an atom is determined based on the number of electrons lost, gained, or shared with another atom at the time of bond formation.

An atom is said to be stable when its outermost shells have eight electrons (except H & He). If the total number of electrons in outermost shells is between one to four, the atom has positive valency and if electrons are between four to eight, the valency is calculated by subtracting from eight and valency will be zero. Atoms having four outermost electrons possess both positive and negative valency, and atoms having eight outermost electrons, valency will be zero (i.e. noble gases).

Noble gases like argon have eight valence electrons so it does not require to lose or gain electrons to complete its energy shell i.e. stable octet. So that they do not have any tendency to combine with other elements which makes the valency of argon zero. Because valency is all about lose, gain, or share of electrons.

We can also find the valency of argon with the help of the periodic table. As argon belongs to group 8A which are groups of noble gases having valency zero.