Question

Properties of the elements are given below. Where would you locate the following elements in the periodic table?

An element with variable (more than one) valency stored underwater

Answer 1

Element with variable valency stored underwater:

• The atomic number of phosphorous is 15 and the electronic configuration is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^3$.
• Phosphorous can accept either 3 electrons or donate 5 electrons depending on the neighborhood element, that is it has variable valency.
• It readily catches fire in the air to give dense white fumes of phosphorus oxide $\left({\mathrm{P}}_4{\mathrm{O}}_{10}\right)$​.
• Hence, it is kept in water to avoid oxidation by the oxygen present in the air.
• Phosphorous is kept in water because it is insoluble in water.
• Phosphorous is in the third period and group 15.

Therefore, an element with variable valency stored underwater is phosphorous, it is in the third period and group 15.