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.
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