Inert pair effect (heavier p-block) (For heavier p-block elements, the ns² electron pair is more inert: Tl⁺, Pb²⁺, Bi³⁺)
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For heavier p-block elements, the ns² electron pair is more inert — Tl⁺, Pb²⁺, Bi³⁺ stabilized vs higher oxidation states.
What each symbol means
| Symbol | What it stands for |
|---|---|
| np | p valence electrons |
| ns² | Inner s valence pair |
When to use this
Relativistic contraction and poor shielding make ns² reluctant to participate in bonding for heavy elements.