Question

List the elements having variable valency $1\mathrm{and}3$?

Answer 1

Valency:

• An element's valency is determined as the number of electrons in an element's outer shell which defines the measure of its ability to combine with other atoms to form chemical compounds or molecules.
• The valency of elements in the periodic table is the same for a particular group.

Variable valency:

• Elements having more than one valency are known as variable valency.
• When the metals donate electrons from their inner valence shell along with their outer valence shell, they said to attain multiple valencies or variable valencies.
• Mostly the transition metals having more number of electrons in their outer d orbital, exhibit variable valency.

The list of elements having variable valency $\mathbf{1}\mathbf{}\mathbf{and}\mathbf{}\mathbf{3}$:

• The elements Thallium and Gold have valencies of $1\mathrm{and}3$
• The electron configuration of thallium is given as : $\left[\mathrm{Xe}\right]6{\mathrm{s}}^{2}4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}6{\mathrm{p}}^1$
• Hence, it is easy to remove the $6\mathrm{p}$ electron and form ${\mathrm{Tl}}^{+}$.
• Next by removing $6{\mathrm{s}}^2$ electrons it gives ${\mathrm{Tl}}^{3+}$ .
• Similarly, the electron configuration of gold is $\left[\mathrm{Xe}\right]6{\mathrm{s}}^{1}4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}.$
• Hence the removal of the $6\mathrm{s}$ electron and form ${\mathrm{Au}}^{+}$.
• Also by removing the next $5\mathrm{d}$ subshell electrons of gold it gives ${\mathrm{Au}}^{3+}$.

Hence, the list of the elements having variable valency $1\mathrm{and}3$ are given as: Thallium and Gold.