Question

An element X has valency 1.

(i) Write the chemical formula of its phosphide.
(ii) Is element X a metal or a non-metal?
[2 Marks]

Answer 1

(i) Valency of element X = 1
Valency of phosphide ion, $P^{3-}$ = 3

Symbol	X	P
Valency	1	3

Upon criss-crossing the valencies, we get the chemical formula as $X_{3}P$.

[1 Mark]

(ii) While writing the chemical formula, the name/symbol of metal is written first followed by the non-metal. Since phosphide ion is of a non-metal forming anion, $P^{3-}$ ion is written after writing $X^{+}$. Therefore, element X is a metal.

[1 Mark]