Q10.4P - Chemistry: Molecular Nature Of Matter And Change

Question

What is required for an atom to expand its valence shell?

Which of the following atoms can expand its valence shell: F, S, H, Al, Se, Cl?

 

Step-by-Step Solution

Answer

S, Al, Se and Cl can expand their valence shell as they have an empty d-orbital in the valence shell of each atom.

This is the reason that they can accommodate more electrons and form a large molecule.

 

Step 1: Valence Shell

A valence shell may be defined as the outermost shell of an atom, which is required to bond with another atom. There is some valence shell in the atom which can acquire electrons.

For example, the electronic Configuration of Fluorine having an atomic number 9 is,

 

 $\mathbf{Fluorine}\mathbf{,}\mathbf{F}\mathbf{=}\mathbf{1}{\mathbf{s}}^2\mathbf{2}{\mathbf{s}}^2\mathbf{2}{\mathbf{p}}^5$

Step 2: Explanation

As per the electronic configuration of each atom, it can be found easily that the H carries only s-orbital and F has filled valence p-orbital.

Therefore because of the absence of any vacant orbitals in the valence shell they cannot expand i.e., the electron cannot move to the next shell.

 

$\begin{array}{l}\mathbf{Fluorine}\mathbf{,}\mathbf{F}\mathbf{=}\mathbf{1}{\mathbf{s}}^2\mathbf{2}{\mathbf{s}}^2\mathbf{2}{\mathbf{p}}^5\\ \mathbf{Hydrogen}\mathbf{,}\mathbf{H}\mathbf{=}\mathbf{1}{\mathbf{s}}^1\end{array}$

 

On the other hand, S, Al, Se and Cl have empty d-orbitals in the outer shell and hence they can accommodate another atom/molecule.

Because of the empty d-orbital, they can bond more than one atom and form a complex molecule and can expand.

 $\begin{array}{l}\mathbf{Sulfur}\mathbf{,}\mathbf{S}\mathbf{=}\mathbf{1}{\mathbf{s}}^2\mathbf{2}{\mathbf{s}}^2\mathbf{2}{\mathbf{p}}^6\mathbf{3}{\mathbf{s}}^2\mathbf{3}{\mathbf{p}}^{4}3{\mathrm{d}}^0\\ \mathbf{Aluminium}\mathbf{,}\mathbf{Al}\mathbf{=}\mathbf{1}{\mathbf{s}}^2\mathbf{2}{\mathbf{s}}^2\mathbf{2}{\mathbf{p}}^6\mathbf{3}{\mathbf{s}}^2\mathbf{3}{\mathbf{p}}^{1}3{\mathrm{d}}^0\\ \mathbf{Selenium}\mathbf{,}\mathbf{Se}\mathbf{=}\mathbf{1}{\mathbf{s}}^2\mathbf{2}{\mathbf{s}}^2\mathbf{2}{\mathbf{p}}^6\mathbf{3}{\mathbf{s}}^2\mathbf{3}{\mathbf{p}}^6\mathbf{3}{\mathbf{d}}^{10}\mathbf{4}{\mathbf{s}}^2\mathbf{4}{\mathbf{p}}^{4}4{\mathrm{d}}^0\\ \mathbf{Chlorine}\mathbf{,}\mathbf{Cl}\mathbf{=}\mathbf{1}{\mathbf{s}}^2\mathbf{2}{\mathbf{s}}^2\mathbf{2}{\mathbf{p}}^6\mathbf{3}{\mathbf{s}}^2\mathbf{3}{\mathbf{p}}^{5}3{\mathrm{d}}^0\end{array}$

 

The atom can expand its valence shell only if its electron can get energised and simultaneously move to the other orbital in a cycle.