11 elements
Post-transition metals
The post-transition metals sit between the transition metals and the metalloids. They are softer, with lower melting points than transition metals, and their bonding has more covalent character. Aluminium, tin and lead are the best-known members.
- Members
- 11
- At room temp
- 11 solid
- Melting range
- 30 to 660 °C
- Electronegativity
- 1.61 – 2.33
All post-transition metals
- 13AlAluminium26.9815 u · 1825
- 31GaGallium69.723 u · 1875
- 49InIndium114.818 u · 1863
- 50SnTin118.71 u · c. 3500 BCE
- 81TlThallium204.383 u · 1861
- 82PbLead207 u · c. 7000 BCE
- 83BiBismuth208.9804 u · 1753
- 113NhNihonium[286] u · 2004
- 114FlFlerovium[290] u · 1998
- 115McMoscovium[290] u · 2003
- 116LvLivermorium[293] u · 2000
A softer kind of metal
To the right of the transition block, before the staircase of metalloids, sits a small group of metals that behave differently from their neighbours. They are softer and weaker, with lower melting points, and their compounds often have partly covalent bonds. Gallium melts in your hand, and tin and lead have been cast into shapes since ancient times for exactly this reason.
Chemists do not agree on exactly which elements belong here, and the name itself varies: they are also called poor metals or other metals. This site includes aluminium, gallium, indium, tin, thallium, lead and bismuth, along with four superheavy elements, nihonium, flerovium, moscovium and livermorium, whose properties are mostly predicted.
Aluminium, the surprising one
Aluminium is the most abundant metal in the Earth’s crust, yet it was only isolated in 1825 and for decades was more precious than gold. Napoleon III is said to have served his most honoured guests on aluminium plates. Everything changed in 1886, when the Hall–Héroult electrolysis process made it cheap.
Aluminium is reactive, but a thin, tough layer of oxide forms instantly on its surface and protects it. That is why it can be used for drinks cans, window frames and aircraft without corroding.
Metals with a toxic side
Lead and thallium are poisonous. Lead was once used in water pipes, paint and petrol, and its removal from those uses is one of the great public health successes of the last century. Thallium was a notorious poison because it is tasteless and odourless.
Bismuth, sitting next to lead, is the exception: it is remarkably harmless and is the active ingredient in some stomach remedies.
The members compared
| Element | State | Density | Electronegativity | Discovered |
|---|---|---|---|---|
| Aluminium | Solid | 2.7 g/cm³ | 1.61 | 1825 |
| Gallium | Solid | 5.91 g/cm³ | 1.81 | 1875 |
| Indium | Solid | 7.31 g/cm³ | 1.78 | 1863 |
| Tin | Solid | 7.287 g/cm³ | 1.96 | c. 3500 BCE |
| Thallium | Solid | 11.8 g/cm³ | 1.62 | 1861 |
| Lead | Solid | 11.342 g/cm³ | 2.33 | c. 7000 BCE |
| Bismuth | Solid | 9.807 g/cm³ | 2.02 | 1753 |
| Nihonium(Predicted) | Solid | 16 g/cm³ | — | 2004 |
| Flerovium(Predicted) | Solid | 14 g/cm³ | — | 1998 |
| Moscovium(Predicted) | Solid | 13.5 g/cm³ | — | 2003 |
| Livermorium(Predicted) | Solid | 12.9 g/cm³ | — | 2000 |
Small amounts, big technology
Several of these metals are critical to electronics. Indium tin oxide forms the transparent, conducting layer on every touchscreen. Gallium arsenide and gallium nitride make LEDs, lasers and fast chips. Tin is the main ingredient in the solder that joins components on circuit boards.
Frequently asked questions
Why are post-transition metals called poor metals?
Compared with transition metals they are softer, weaker and have lower melting points, and their bonding is less purely metallic. “Poor” refers to these weaker metallic properties.
Which post-transition metal melts at the lowest temperature?
Gallium, which melts at 29.8 °C, just above room temperature. It stays liquid up to about 2,400 °C, one of the widest liquid ranges of any element.
Is aluminium a post-transition metal?
Yes. It sits in group 13, right of the transition block and left of the metalloids, and shares the typical features: low density, a low melting point compared with transition metals and partly covalent compounds.