Q49 E - Chemistry (OpenStax)

Question

Explain why N₂²⁺ is diamagnetic, while O₂⁴⁺, which has the same number of valence electrons, is paramagnetic.

Step-by-Step Solution

Answer

∏p Orbital in O₂⁴⁺ contains two unpaired electrons so paramagnetic. The ∏p orbital in N₂²⁺ is fully filled so diamagnetic

Step 1: Define valence electron

A valence electron is the most probable electron to be involved in a chemical process. The electrons having the largest value of the primary quantum number, n, are usually those.

Step 2: Explanation

This is because,

N₂²⁺: (σ_2s)² (σ ^*_2s)² (∏2py∏2pz)⁴(σ⁰ _2px)

O₂⁴⁺ : (σ_2s)² (σ ^*_2s)² (σ _2px)² (∏2py∏2pz)²

The σ_p orbital is lifted above the ∏p, set due to s-p mixing in N₂, whereas there is no s-p mixing in O₂ and it will follow the regular pattern.

As a result, σ_p orbital will fill before ∏p, orbital in O_2, and ∏p, orbital in O₂⁴⁺ has two unpaired electrons and is paramagnetic. The ∏p orbital in the N₂²⁺ is completely filled and it is diamagnetic.