Arrange the bonds in order of increasing ionic character in the molecules. LiF, K₂ O, N₂, SO₂ and ClF₃ :

Solution

Chemistry ma’am · 4 steps

Rank each bond by the electronegativity gap between its two atoms. A bigger gap means more ionic character.

1. The rule. Ionic character grows with the electronegativity difference Δχ between the bonded atoms. Zero difference gives a pure covalent bond, and a large difference (about 2 or more) gives a mainly ionic bond.

   Bond	Electronegativity gap	Nature
   N-N in N₂	0, identical atoms	pure covalent
   S-O in SO₂	about 1	polar covalent
   Cl-F in ClF₃	about 1, and the partner is F	polar covalent
   K-O in K₂O	3.4 - 0.8 = 2.6	ionic
   Li-F in LiF	4.0 - 1.0 = 3.0	most ionic

2. The close pair. S-O and Cl-F are both polar covalent bonds with similar gaps. The Cl-F bond is taken as the more polar one because fluorine is the most electronegative element. On the Allred–Rochow scale the gaps come out near 1.3 for Cl-F and 1.1 for S-O.
3. The ionic pair. Both K₂O and LiF pair a metal with a non-metal. LiF has the larger gap because F is more electronegative than O, so it comes last.
4. So. The increasing order is N₂ < SO₂ < ClF₃ < K₂O < LiF, which is option (a).

The idea to keep. For ionic character, look only at the electronegativity gap across the bond. Identical atoms give zero, non-metal pairs sit in the middle, and metal with F or O sits at the top.

Answer from the NTA final answer key. Solution by PrepWiser.