Question

What is the covalency of $\mathrm{Cl}$ in its second excited state?

Answer 1

Covalency:

• The number of covalent bonds that can be formed by an atom is known as covalency.

Chlorine:

• Chlorine is a halogen with an atomic number $17$

For covalency of chlorine:

• Electronic configuration of chlorine:

$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^5$ or$\left[\mathrm{Ne}\right]3{\mathrm{s}}^{2}3{\mathrm{p}}^5$, where $\mathrm{Ne}=$ Neon

• In the first excited state the electronic configuration will be:

$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{4}3{\mathrm{d}}^1$

• The electronic configuration in the second excited state will be:

$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{3}3{\mathrm{d}}^2$

• As there are five unpaired electrons in the second excited state of chlorine, thus the covalency of chlorine in the second excited state will be $5$.
• It can be understood by the below diagram where GS is the ground state and ES is the excited state.