Sulfur vs Phosphorus
Both are polyatomic non-metals, so they share the same broad chemistry.
The differences in plain English
- They share period 3, the same row, so their outer electrons are in the same shell but they differ in how many there are: Sulfur has 6, Phosphorus has 5.
- Both are solids at room temperature.
- Sulfur is denser, only slightly more than Phosphorus (2.07 against 1.823 g/cm³).
- An atom of Sulfur is only slightly heavier than an atom of Phosphorus (32.06 u against 30.97 u).
- Sulfur pulls electrons more strongly in a bond (electronegativity 2.58 against 2.19).
Side by side
| Sulfur | Phosphorus | |
|---|---|---|
| Atomic number | 16 | 15 |
| Symbol | S | P |
| Family | Polyatomic non-metal | Polyatomic non-metal |
| Group / period | 16 / 3 | 15 / 3 |
| State at room temperature | Solid | Solid |
| Atomic mass | 32.060 u | 30.974 u |
| Density | 2.07 g/cm³ | 1.823 g/cm³ |
| Melting point | 115 °C | – |
| Boiling point | 445 °C | – |
| Electronegativity | 2.58 | 2.19 |
| First ionisation energy | 999.6 kJ/mol | 1011.8 kJ/mol |
| Electron configuration | [Ne] 3s2 3p4 | [Ne] 3s2 3p3 |
| Discovered by | Ancient china | Hennig Brand |
Sulfur
Sulfur is one of the few elements you can pick up straight out of the ground and recognise. Around volcanic vents it forms bright yellow crusts, and a lump of it burns with a blue flame and a sharp, choking smell. People have known it for thousands of years, long before anyone had the idea of a chemical element.
- Sulfur has more solid forms, or allotropes, than any other element; the familiar yellow crystals are made of rings of eight atoms.
- When molten sulfur is heated further it becomes darker and thicker instead of thinner, because the rings break open and tangle into long chains.
Phosphorus
Phosphorus was the first element discovered by a person whose name we know, and it arrived with a sense of theatre. In 1669 a German alchemist boiled down vast quantities of urine and obtained a waxy solid that glowed in the dark and burst into flame in air. He named it after the Greek for light-bearer.
- Phosphorus was the first element discovered by a named individual, Hennig Brand, in about 1669.
- White phosphorus glows in the dark because it reacts slowly with oxygen in the air, not because it stores light.
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.