Boron vs Aluminium
Boron is a metalloid (metalloid); Aluminium is a metal (post-transition metal).
The differences in plain English
- They sit in the same column, group 13, so they have the same number of outer electrons and react in similar ways; the heavier one, Aluminium, is usually the more reactive of the two if they are metals, and the less reactive if they are non-metals.
- Both are solids at room temperature.
- Aluminium is denser, about 30 per cent more than Boron (2.7 against 2.08 g/cm³).
- Boron melts at 2076 °C, far above Aluminium at 660 °C.
- An atom of Aluminium is about 2.5 times heavier than an atom of Boron (26.98 u against 10.81 u).
- Boron pulls electrons more strongly in a bond (electronegativity 2.04 against 1.61).
Side by side
| Boron | Aluminium | |
|---|---|---|
| Atomic number | 5 | 13 |
| Symbol | B | Al |
| Family | Metalloid | Post-transition metal |
| Group / period | 13 / 2 | 13 / 3 |
| State at room temperature | Solid | Solid |
| Atomic mass | 10.810 u | 26.982 u |
| Density | 2.08 g/cm³ | 2.7 g/cm³ |
| Melting point | 2076 °C | 660 °C |
| Boiling point | 3927 °C | 2470 °C |
| Electronegativity | 2.04 | 1.61 |
| First ionisation energy | 800.6 kJ/mol | 577.5 kJ/mol |
| Electron configuration | [He] 2s2 2p1 | [Ne] 3s2 3p1 |
| Discovered by | Joseph Louis Gay-Lussac |
Boron
Boron is a dark, brittle, very hard solid that is neither quite a metal nor quite a non-metal. Chemists call it a metalloid. It has three outer electrons, which is not enough to bond in the ordinary ways, so it builds unusual cage-shaped clusters that keep researchers busy to this day. Pure boron is rarely seen outside laboratories, but its compounds are everywhere.
- Boron is one of very few elements not made inside stars. Almost all of it comes from cosmic rays splitting heavier atoms apart.
- Boron compounds burn with a bright green flame, and boric acid is used to colour green fireworks.
Aluminium
Aluminium is the most abundant metal in the Earth's crust, yet two hundred years ago nobody had seen a piece of it. It clings so tightly to oxygen that separating it needed chemistry that did not yet exist. Then cheap electricity changed everything, and today it is the second most used metal in the world.
- In the 1850s aluminium cost more than gold, and Napoleon III is said to have served his most honoured guests with aluminium cutlery.
- The small pyramid on top of the Washington Monument, set in 1884, is made of aluminium, then a showpiece metal.
Colour the bubbles by density or melting point and the difference jumps out.
More comparisons
Data from Periodic-Table-JSON (CC BY-SA); temperatures rounded to the nearest degree. Written by Anthony.