Question

Which combination of atoms can form a polar covalent bond ?

• A. H and H
• B. H and Br
• C. N and N
• D. Na and Br

Answer 1

Answer: (B)

When there is less difference in electronegativities of two atoms (but electronegativities are not same) and large difference in their size, polar covalent bond forms.

(a) $H$ and $H$ : No difference in electronegativities, so form non-polar covalent bond.

(b) $H$ and $Br$ : Small difference in electronegativities and large difference in size. Hence, form polar covalent bond.

(c) $N$ and $N$ : Same electronegativity, so non-polar covalent bond.

(d) $Na$ and $Br$ : Large difference in electronegativities, hence electrovalent bond is formed.