---
title: "Radium (Ra): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/radium.html
description: "Radium (Ra), element 88: atomic mass [226], electron configuration [Rn] 7s², group 2, period 7, s-block alkaline earth metal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
88Ra[226]

# Radium (Ra) – element 88

Radium is a chemical element with the symbol **Ra** and atomic number **88**. It is a alkaline earth metal in group 2 (alkaline earth metals), period 7 of the periodic table (s-block), and is a solid at room temperature.

Radium (Ra) has atomic number 88, atomic mass [226] and electron configuration [Rn] 7s2.

[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)

## Radium facts

| Symbol | Ra |
| --- | --- |
| Atomic number | 88 |
| Atomic mass | [226] |
| Category | alkaline earth metal |
| Group | group 2 (alkaline earth metals) |
| Period | 7 |
| Block | s-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 |
| Noble-gas notation | [Rn] 7s2 |
| Electrons per shell | 2, 8, 18, 32, 18, 8, 2 |
| Valence electrons | 2 |

## Bohr model and shells

Radium has 88 electrons in 7 shells: 2, 8, 18, 32, 18, 8, 2. 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 | 1233 K (959.9 °C) |
| --- | --- |
| Boiling point | 2010 K (1736.8 °C) |
| Density | 5.5 g/cm³ |
| Electronegativity (Pauling) | 0.9 |
| Electron affinity | 9.6485 kJ/mol |
| Ionization energies | 509.3, 979 kJ/mol (1st, 2nd) |
| Discovered by | Pierre Curie |

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 Ra.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of radium?

The atomic mass of radium is [226] (mass number of its longest-lived isotope, since it has no stable isotope).

### What is the electron configuration of radium?

Radium has 88 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s², or [Rn] 7s² in noble-gas notation. Electrons per shell: 2, 8, 18, 32, 18, 8, 2.

### How many valence electrons does radium have?

Radium has 2 valence electrons (group 2).

### Is radium a metal?

Yes. Radium is a alkaline earth metal.

### Where is radium on the periodic table?

Radium is in group 2 (alkaline earth metals), period 7, in the s-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.