Beryllium vs Magnesium
Both are alkaline earth metals, so they share the same broad chemistry.
The differences in plain English
- They sit in the same column, group 2, so they have the same number of outer electrons and react in similar ways; the heavier one, Magnesium, 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.
- Beryllium is denser, only slightly more than Magnesium (1.85 against 1.738 g/cm³).
- Beryllium melts at 1287 °C, far above Magnesium at 650 °C.
- An atom of Magnesium is about 2.7 times heavier than an atom of Beryllium (24.30 u against 9.01 u).
- Beryllium pulls electrons more strongly in a bond (electronegativity 1.57 against 1.31).
Side by side
| Beryllium | Magnesium | |
|---|---|---|
| Atomic number | 4 | 12 |
| Symbol | Be | Mg |
| Family | Alkaline earth metal | Alkaline earth metal |
| Group / period | 2 / 2 | 2 / 3 |
| State at room temperature | Solid | Solid |
| Atomic mass | 9.012 u | 24.305 u |
| Density | 1.85 g/cm³ | 1.738 g/cm³ |
| Melting point | 1287 °C | 650 °C |
| Boiling point | 2469 °C | 1090 °C |
| Electronegativity | 1.57 | 1.31 |
| First ionisation energy | 899.5 kJ/mol | 737.7 kJ/mol |
| Electron configuration | [He] 2s2 | [Ne] 3s2 |
| Discovered by | Louis Nicolas Vauquelin | Joseph Black |
Beryllium
Beryllium is a hard, grey metal that combines two properties engineers rarely get together: it is very light and very stiff. It resists bending better than steel while weighing about a quarter as much. It is also transparent to X-rays, an excellent conductor of heat, and hard to find. Beryllium is one of the rarer elements in the Earth's crust and is expensive to refine.
- Emerald and aquamarine are both the mineral beryl, a beryllium aluminium silicate. Traces of chromium make emerald green and traces of iron make aquamarine blue.
- James Chadwick discovered the neutron in 1932 by firing alpha particles at a beryllium target.
Magnesium
Magnesium is a light, silvery metal best known for the dazzling white flame it produces when it burns. Yet the same element, in a gentler form, sits at the centre of the chlorophyll molecule that lets plants capture sunlight. Without it there would be no photosynthesis, and so no food.
- Every chlorophyll molecule has a magnesium ion at its centre, so photosynthesis depends on magnesium.
- Burning magnesium cannot be extinguished with water or carbon dioxide because it reacts with both.
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.