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

Hint: An electrovalent bond is formed by the attraction of two oppositely charged ions in a compound. In a covalent compound, there is a mutual sharing of electrons between the two combining atoms. In a coordinate covalent bond, there is a mutual sharing of electrons with one atom completely donating its electron pair to the adjacent atom.

Complete step by step answer:
In calcium oxide, the electronic configuration of calcium atom is:
$Ca = 20 = 1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}$
Calcium has two valence electrons in its outermost shell and can readily lose two electrons to attain nearest noble gas configuration.
The electronic configuration of $C{a^{2 + }}$ ion:
$C{a^{2 + }} = 18 = 1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}$
The calcium divalent cation attains the electronic configuration of nearest noble gas i.e Argon and hence, is a stable cation.
In the case of oxygen, the electronic configuration of oxygen atom in its ground state is:
$O = 1{s^2}2{s^2}2{p^4}$
The oxygen atom requires two more electrons to attain the nearest noble gas configuration. Thus the electronic configuration of the bivalent oxygen anion is:
${O^{2 - }} = 1{s^2}2{s^2}2{p^6}$
The oxygen anion attains the electronic configuration of nearest noble gas i.e Neon and hence, is a stable anion.
Thus, we can see that calcium can lose two electrons and oxygen can accept two electrons. Thus, calcium gives its two valence electrons to oxygen and forms an electrovalent bond with oxygen, thus completing each other’s octet configuration as well.

Thus, the correct option is B. Electrovalent compound .

Note:
The order of the bond strength from weakest to strongest follows: Van der Waals, Hydrogen, Ionic, Covalent. The strength of covalent bond is greater than the ionic bond because in a covalent bond there is a mutual sharing of valence electrons but in an ionic bond there is a transfer of valence electrons in the outermost shell.