---
title: "Calcium (Ca): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/calcium.html
description: "Calcium (Ca), element 20: atomic mass 40.078, electron configuration [Ar] 4s², group 2, period 4, s-block alkaline earth metal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
20Ca40.078

# Calcium (Ca) – element 20

Calcium is a chemical element with the symbol **Ca** and atomic number **20**. It is a alkaline earth metal in group 2 (alkaline earth metals), period 4 of the periodic table (s-block), and is a solid at room temperature.

Calcium (Ca) has atomic number 20, atomic mass 40.078 u and electron configuration [Ar] 4s2.

[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)

## Calcium facts

| Symbol | Ca |
| --- | --- |
| Atomic number | 20 |
| Atomic mass | 40.078 u (g/mol) |
| Category | alkaline earth metal |
| Group | group 2 (alkaline earth metals) |
| Period | 4 |
| Block | s-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 |
| Noble-gas notation | [Ar] 4s2 |
| Electrons per shell | 2, 8, 8, 2 |
| Valence electrons | 2 |

## Bohr model and shells

Calcium has 20 electrons in 4 shells: 2, 8, 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 | 1115 K (841.9 °C) |
| --- | --- |
| Boiling point | 1757 K (1483.8 °C) |
| Density | 1.55 g/cm³ |
| Electronegativity (Pauling) | 1 |
| Electron affinity | 2.37 kJ/mol |
| Ionization energies | 589.8, 1145.4, 4912.4 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 25.929 J/(mol·K) |
| Discovered by | Humphry Davy |

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 Ca.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of calcium?

The atomic mass of calcium is 40.078 u, so one mole of calcium atoms weighs 40.078 g.

### What is the electron configuration of calcium?

Calcium has 20 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s², or [Ar] 4s² in noble-gas notation. Electrons per shell: 2, 8, 8, 2.

### How many valence electrons does calcium have?

Calcium has 2 valence electrons (group 2).

### Is calcium a metal?

Yes. Calcium is a alkaline earth metal.

### Where is calcium on the periodic table?

Calcium is in group 2 (alkaline earth metals), period 4, 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.