Atomic number of calcium is 20 and of oxygen is 8. State the number of electrons - calcium loses and oxygen gains to attain stable electronic configuration of the nearest noble gas - during formation of electrovalent molecule, calcium oxide.

Calcium oxide is formed as a result of transfer of two valence electrons

• from metallic calcium atom ⁴⁰₂₀Ca; electronic configuration - 2,8,8,2 ; Nearest noble gas = Argon [2,8,8,]
• to non-metallic oxygen atom ¹⁶₈O - electronic configuration - 2,6 ; Nearest noble gas = Neon [2,8]
• calcium loses two electrons - from it's outer shell to attain stability of nearest noble gas - argon and becomes a calcium ion [cation] : Ca²⁺
• oxygen accepts two electrons - in outer shell to attain stability of nearest noble gas - neon and becomes an oxide ion [anion] : O^2-