Number of molecules/ions from the following in which the central atom is involved in sp³ hybridization is ________.
NO₃⁻, BCl₃, ClO₂⁻, ClO₃⁻

Solution

Chemistry ma’am · 3 steps

Sigma bonds plus lone pairs on the centre: four means sp³, three means sp².

1. Steric number. Hybridisation depends on the number of sigma bonds plus lone pairs on the central atom. Pi bonds do not count. A total of 3 gives sp² and a total of 4 gives sp³.

   SN = 1/2(V + M - C + A)

2. What the letters mean. V is the number of valence electrons of the central atom. M is the number of monovalent atoms attached (H or halogen), and oxygen counts as 0. C is the positive charge and A is the negative charge.

   Species	Steric number	Sigma bonds, lone pairs	Hybridisation
   NO₃⁻	1/2(5 + 0 + 1) = 3	3, 0	sp²
   BCl₃	1/2(3 + 3) = 3	3, 0	sp²
   ClO₂⁻	1/2(7 + 0 + 1) = 4	2, 2	sp³
   ClO₃⁻	1/2(7 + 0 + 1) = 4	3, 1	sp³

3. So. Only ClO₂⁻ and ClO₃⁻ have an sp³ central atom. Their lone pairs on chlorine make the steric number 4. The count is 2.

The idea to keep. Hybridisation counts lone pairs too, not just bonded atoms. A bent or pyramidal shape with lone pairs can still be sp³. Always find sigma bonds plus lone pairs first.

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