Post-Transition Metals
The softer metals of the p-block, such as aluminium, gallium, indium, tin, thallium, lead and bismuth.
13AlAluminum31GaGallium49InIndium50SnTin81TlThallium82PbLead83BiBismuth84PoPolonium113NhNihonium114FlFlerovium115McMoscovium116LvLivermorium117TsTennessine
What they have in common
These metals sit between the transition metals and the metalloids. They are metallic, but with lower melting points, softer structures and more covalent character in their compounds than the d-block metals.
The heavier ones show the inert pair effect: the ns² electrons become reluctant to take part in bonding, so lead is most stable as Pb²⁺ rather than Pb⁴⁺, and thallium prefers Tl⁺.
- Soft, with low melting points (gallium melts in your hand at 303 K)
- Amphoteric oxides for Al, Sn and Pb
- Inert pair effect in heavier members
Post-transition metals at a glance
| Element | Z | Mass | Configuration | Valence e⁻ | Charges | EN | Radius (pm) |
|---|---|---|---|---|---|---|---|
| Aluminum (Al) | 13 | 26.982 | [Ne] 3s2 3p1 | 3 | 3+ | 1.61 | 118 |
| Gallium (Ga) | 31 | 69.723 | [Ar] 3d10 4s2 4p1 | 3 | 3+ | 1.81 | 126 |
| Indium (In) | 49 | 114.818 | [Kr] 4d10 5s2 5p1 | 3 | 3+ | 1.78 | 144 |
| Tin (Sn) | 50 | 118.71 | [Kr] 4d10 5s2 5p2 | 4 | 2+, 4+ | 1.96 | 141 |
| Thallium (Tl) | 81 | 204.383 | [Xe] 4f14 5d10 6s2 6p1 | 3 | +, 3+ | 2.04 | 148 |
| Lead (Pb) | 82 | 207.2 | [Xe] 4f14 5d10 6s2 6p2 | 4 | 2+, 4+ | 2.33 | 147 |
| Bismuth (Bi) | 83 | 208.98 | [Xe] 4f14 5d10 6s2 6p3 | 5 | 3+ | 2.02 | 146 |
| Polonium (Po) | 84 | [209] | [Xe] 4f14 5d10 6s2 6p4 | 6 | 2+, 4+ | 2 | — |
| Nihonium (Nh) | 113 | [284] | [Rn] 5f14 6d10 7s2 7p1 | 3 | — | — | — |
| Flerovium (Fl) | 114 | [289] | [Rn] 5f14 6d10 7s2 7p2 | 4 | — | — | — |
| Moscovium (Mc) | 115 | [288] | [Rn] 5f14 6d10 7s2 7p3 | 5 | — | — | — |
| Livermorium (Lv) | 116 | [293] | [Rn] 5f14 6d10 7s2 7p4 | 6 | — | — | — |
| Tennessine (Ts) | 117 | [294] | [Rn] 5f14 6d10 7s2 7p5 | 7 | — | — | — |
Questions students ask
Which elements are post-transition metals?
Commonly Al, Ga, In, Sn, Tl, Pb and Bi, with Nh, Fl, Mc, Lv and Ts expected to fit. Classification varies between textbooks, especially for polonium and astatine.