---
title: "Phosphorus (P): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/phosphorus.html
description: "Phosphorus (P), element 15: atomic mass 30.974, electron configuration [Ne] 3s² 3p³, group 15, period 3, p-block reactive nonmetal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
15P30.974

# Phosphorus (P) – element 15

Phosphorus is a chemical element with the symbol **P** and atomic number **15**. It is a reactive nonmetal in group 15 (pnictogens), period 3 of the periodic table (p-block), and is a solid at room temperature.

Phosphorus (P) has atomic number 15, atomic mass 30.974 u and electron configuration [Ne] 3s2 3p3.

[Download periodic table PDF](https://www.moldraw.com/printables/periodic-table.pdf)[Open interactive periodic table](https://www.moldraw.com/tools/free-chem-tools/interactive-periodic-table.html)

## Phosphorus facts

| Symbol | P |
| --- | --- |
| Atomic number | 15 |
| Atomic mass | 30.974 u (g/mol) |
| Category | reactive nonmetal |
| Group | group 15 (pnictogens) |
| Period | 3 |
| Block | p-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p3 |
| Noble-gas notation | [Ne] 3s2 3p3 |
| Electrons per shell | 2, 8, 5 |
| Valence electrons | 5 |

## Bohr model and shells

Phosphorus has 15 electrons in 3 shells: 2, 8, 5. Full configuration and noble-gas notation are in the table; work out any element or ion with the [electron configuration calculator](https://www.moldraw.com/tools/free-chem-tools/electron-configuration-calculator.html).

## Physical and atomic properties

| Melting point | 317.3 K (44.2 °C) |
| --- | --- |
| Density | 1.823 g/cm³ |
| Electronegativity (Pauling) | 2.19 |
| Electron affinity | 72.037 kJ/mol |
| Ionization energies | 1011.8, 1907, 2914.1 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 23.824 J/(mol·K) |
| Discovered by | Hennig Brand |

Use the atomic mass in the [molar mass calculator](https://www.moldraw.com/tools/free-chem-tools/molar-mass-calculator.html) for any formula containing P.

## Position in the periodic table

Tap any element to open its page.

## Molecules with phosphorus

- [ATP](https://www.moldraw.com/molecules/atp.html)

Rotate each one in 3D, or draw your own structure in [MolDraw](https://www.moldraw.com/).

## Frequently asked questions

### What is the atomic mass of phosphorus?

The atomic mass of phosphorus is 30.974 u, so one mole of phosphorus atoms weighs 30.974 g.

### What is the electron configuration of phosphorus?

Phosphorus has 15 electrons: 1s² 2s² 2p⁶ 3s² 3p³, or [Ne] 3s² 3p³ in noble-gas notation. Electrons per shell: 2, 8, 5.

### How many valence electrons does phosphorus have?

Phosphorus has 5 valence electrons (group 15).

### Is phosphorus a metal?

No. Phosphorus is a nonmetal (reactive nonmetal).

### Where is phosphorus on the periodic table?

Phosphorus is in group 15 (pnictogens), period 3, in the p-block.

Data: [Periodic-Table-JSON](https://github.com/Bowserinator/Periodic-Table-JSON) (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.