Complete the table given below for writing the formula of a chemical compound.

Identify the valency	Criss cross the valency	Formula of the compound	Name of the compound
$\mathrm{Ca}$ $\mathrm{N}$	$\mathrm{Ca}$ $\mathrm{N}$

Part 1: Identify the valency of $\mathrm{Ca}$ and $\mathrm{N}$:

• The calcium atom $\mathbf{\left(}\mathbf{Ca}\mathbf{\right)}$ loses two electrons from the outermost shell and forms calcium ion with two positive charges $\mathbf{\left(}{\mathbf{Ca}}^{\mathbf{2}\mathbf{+}}\mathbf{\right)}$.
• Thus, the valency of $\mathrm{Ca}$ is $2$.
• The nitrogen atom $\mathbf{\left(}\mathbf{N}\mathbf{\right)}$ gains three electrons in the outermost shell and forms nitride ion with three negative charges $\mathbf{\left(}{\mathbf{N}}^{3-}\mathbf{\right)}$.
• Thus, the valency of $\mathrm{N}$ is $3$.

Part 2: Criss-cross the valency:

• The valency of $\mathrm{Ca}$ becomes the number of $\mathrm{N}$ atoms.
• The valency of $\mathrm{N}$ becomes the number of $\mathrm{Ca}$ atoms.

Part 3: Formula of the compound:

• After criss-crossing the valencies, there are three $\mathrm{Ca}$ atoms and two $\mathrm{N}$ atoms.
• Thus, the formula of the compound is ${\mathrm{Ca}}_3{\mathrm{N}}_2$.

Part 4: Name of the compound:

• While naming the ionic compounds, name of cation is written first and then the anion is named.
• Here, the cation is calcium $\mathbf{\left(}{\mathbf{Ca}}^{\mathbf{2}\mathbf{+}}\mathbf{\right)}$ and the anion is nitride $\mathbf{\left(}{\mathbf{N}}^{3-}\mathbf{\right)}$.
• Thus, the name of the compound is Calcium nitride.

Identify the valency	Criss cross the valency	Formula of the compound	Name of the compound
$\mathrm{Ca}$ $\mathrm{N}$ $2$ $3$	$\mathrm{Ca}$ $\mathrm{N}$ $3$ $2$	${\mathrm{Ca}}_3{\mathrm{N}}_2$	Calcium nitride