Question

What kind of compound is $CaO$ or Calcium Oxide.

• A. Covalent compound
• B. Electrovalent compound
• C. Co-ordinate covalent compound
• D. None of these

Answer 1

Answer: (B)

Electrovalent compound

$CaO$ is an electrovalent compound.
In $CaO$, Calcium has $20$ electrons, and its electronic configuration can be written as $2,8,8,2$. Oxygen has $8$ electrons, and its electronic configuration can be written as $2,6$.
Thus, we see that $Ca$ has two electrons in its outermost orbit or it can be said that there are $2$ valence electrons in Calcium. Calcium wants to give away these two electrons to complete its octet by attaining the electronic configuration of its nearest inert gas Argon.
$O$ has six electrons in its outermost orbit, or it can be said that Oxygen has $6$ valence electrons. It requires two electrons more to complete its octet by attaining the electronic configuration of its nearest inert gas Neon.
So, we see that Calcium wants to lose $2$ electrons and Oxygen wants to gain $2$ electrons. Thus Calcium gives its two valence electrons to Oxygen and an ionic bond is formed between them.
Hence Calcium Oxide is an ionic or electrovalent compound.
An electrovalent compound is formed when one atom transfers one or more electrons from itself to its neighboring atom, and an ionic bond is formed between the two atoms of the compound.
In Calcium Oxide, Calcium transfers its two valence electrons to its neighbour Oxygen and an ionic bond is formed between them.
Thus $CaO$ is an ionic or electrovalent compound.