Question

Neon and chlorine have atomic numbers 10 and 17 respectively. Their valencies will be ______ and ______ respectively.

• A. 0
• B. 1

Answer 1

Valency:-

1. This is actually defined as the combining capacity of the atoms or the molecules.
2. It is obtained from the number of electrons that must be present in the outermost shell of an atom.
3. So, if the electrons present in the outermost shell is 4 or less, then the valency would be same as those number of electrons.
4. If the electrons present in the outermost shell is greater than 4, then the valency would be the difference between the total number of electrons present in the outermost shell and 8.
5. Valency of chlorine:- Chlorine is a halogen whose atomic number is = $17$ , having the electronic configuration as:- $\mathrm{Cl}(\mathrm{Z}=17):1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^5$
6. This will depict the electronic configuration of Chlorine as (2, 8, 7), so $\mathrm{Cl}$ will attain one electron for the attainment of the stable noble gas configuration.
7. For Valency of Neon:- Neon is actually a noble gas that will have the complete outer shell, so it will not lose, share or gain any electron.
8. Noble gases are basically inert in nature and do not tend to lose electron or do not take part in any chemical reaction.
9. So, the valency of the inert gases is zero.
10. The electronic configuration for Neon $\mathrm{Ne}(\mathrm{Z}=10)1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6$.

Therefore, The valencies of Neon and Chlorine will be 0 and 1 respectively.