Give one example of a monovalent monoatomic cation.

Cation:

• It is defined as a positively charged ion that is formed when an atom losses its electron (usually valence electron).
• Since the ion formed is having more number of protons than electrons, hence carries a net positive charge.
• Example of cation is ${\mathrm{Na}}^{+}$which is formed when the outer valence electron of sodium atom is removed.

Monovalent cation:

• An atom that loses only one electron and acquires net $+1$ positive charge is called a monovalent cation.
• Example; potassium ion (${\mathrm{K}}^{+}$), sodium ion (${\mathrm{Na}}^{+}$) etc.

Monoatomic cation:

• An ion with a net positive charge which consists of exactly one atom is called a monoatomic cation.
• Example; sodium ion (${\mathrm{Na}}^{+}$), calcium ion (${\mathrm{Ca}}^{2+}$) etc.

Thus, the example of a monovalent monoatomic cation is sodium ion (${\mathbf{Na}}^{\mathbf{+}}$).