Question

How are ions formed ?Illustrate with suitable examples the formation of cations and anions.

Answer 1

Definition

• Sometimes atoms will gain or lose electrons and form ions.
• Whenever an atom gain electrons it forms a negatively charged ion which is called an anion.
• Whenever an atom loses electrons it forms a positively charged ion which is called a cation.

Example

• Neutral Sodium atom ($\mathrm{Na}$) becomes Sodium Cation (${\mathrm{Na}}^{+}$) by losing one electron.
• Atomic number of Sodium ( $\mathrm{Na}$) = 11
• Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M} \\ 281 \end{gathered}$$
• Valence electrons of Sodium = $1$
• By losing one electron Sodium atom will have filled the outermost orbit.
• Electronic configuration of Sodium cation (${\mathrm{Na}}^{+}$) = $$\begin{gathered} \mathrm{K}\mathrm{L} \\ 28 \end{gathered}$$
• By accepting one electron, neutral Chlorine ($\mathrm{Cl}$) atom forms a Chloride anion (${\mathrm{Cl}}^{-}$).
• Atomic number of Chlorine ( $\mathrm{Cl}$) = 17
• Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M} \\ 287 \end{gathered}$$
• Valence electrons of Chlorine = 7
• By gaining one electron Chlorine atom will complete its octet.
• Electronic configuration of Chloride anion (${\mathrm{Cl}}^{-}$) = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M} \\ 288 \end{gathered}$$