Question

Valency of silver in $A{g}_{2}S$ is .
A. 1
B. 2
C. 0
D. 3

Answer 1

Hint: The valency of an element is referred to as the combining capacity of an element with other elements to form a compound . Also , a single element can have multiple valencies when it combines with different elements .

Complete step by step answer: To find out the valency of silver in a given compound let us first assume valency of silver to be x .
Now , we know that valency of sulphur is -2 since the electronic configuration of sulphur is $1s^{2}2s^{2}2p^{6}3s^{2}3p_x^{2}3p_y^{1}3p_z^1$ it can gain two electrons to complete its octet .
Since the molecule is neutral, the charge on the molecule is 0 .
$$\begin{gathered} 2\times x+(-2)=0 \\ \Rightarrow 2x=2 \\ \Rightarrow x=1 \end{gathered}$$
Hence we find out that the valency of silver in $A{g}_{2}S$ is + 1 .
So , option A is correct.

Additional Information: Silver belongs to group 11 and 5th period , it is a transition metal with atomic number 47.
The electronic configuration of silver is $[Kr]4d^{10}5s^1$ and electrons in each shell are 2 , 8 , 18 , 18 , 1.
Generally the valency of silver is + 1 , as the d sub - shell has stable configuration if they lose 1 electron from s sub - shell . therefore the most common valency of silver is 1 . But there are a few exceptions where it exhibits + 2 valency , when it loses electrons from the d sub - shell to exhibit transition property of metals.
Thus silver shows two valencies +1 and +2 but +1 is more stable and common.

Note: Alternative way to find out valency of an element is by counting the number of electrons in its outermost shell .
If the number of electrons is between one to four , the compound has positive valency equal to the number of electrons in the outermost shell . For compounds having more than four electrons valency is determined by subtracting the number of electrons from eight.