Lithium vs Sodium
Both are alkali metals, so they share the same broad chemistry.
The differences in plain English
- They sit in the same column, group 1, so they have the same number of outer electrons and react in similar ways; the heavier one, Sodium, 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.
- Sodium is denser, about 81 per cent more than Lithium (0.968 against 0.534 g/cm³).
- Lithium melts at 180 °C, Sodium at 98 °C.
- An atom of Sodium is about 3.3 times heavier than an atom of Lithium (22.99 u against 6.94 u).
- Lithium pulls electrons more strongly in a bond (electronegativity 0.98 against 0.93).
Side by side
| Lithium | Sodium | |
|---|---|---|
| Atomic number | 3 | 11 |
| Symbol | Li | Na |
| Family | Alkali metal | Alkali metal |
| Group / period | 1 / 2 | 1 / 3 |
| State at room temperature | Solid | Solid |
| Atomic mass | 6.940 u | 22.990 u |
| Density | 0.534 g/cm³ | 0.968 g/cm³ |
| Melting point | 180 °C | 98 °C |
| Boiling point | 1330 °C | 883 °C |
| Electronegativity | 0.98 | 0.93 |
| First ionisation energy | 520.2 kJ/mol | 495.8 kJ/mol |
| Electron configuration | [He] 2s1 | [Ne] 3s1 |
| Discovered by | Johan August Arfwedson | Humphry Davy |
Lithium
Lithium is a soft, silvery metal and the lightest solid element. A lump of it feels oddly weightless in the hand, with roughly half the density of water. It is the first of the alkali metals, the family that fills the left-hand column of the periodic table and reacts eagerly with water.
- Lithium is the lightest metal and the least dense solid element.
- Lithium was one of only three elements created in significant amounts in the Big Bang.
Sodium
Sodium is a metal so soft that it can be cut with a butter knife, and so reactive that a small piece dropped into water fizzes, melts and often bursts into flame. Freshly cut, it is bright silver. Within seconds the surface dulls as it reacts with the air. Nobody meets sodium metal outside a laboratory, but everyone meets its compounds, because one of them is table salt.
- Sodium is soft enough to cut with a knife and floats on water, where it fizzes and often catches fire.
- Sodium street lamps glow orange because excited sodium atoms emit light at a wavelength close to 589 nanometres.
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.