Calcium occurs in limestone and in bones as compounds.
Uses and research
Calcium metal is different from these familiar materials.
A metal and the substances containing it
The alkaline earth metals are in group 2. A pure metal and a compound containing that element can have very different properties. Being present in a rock or material is different from being present as a lump of metal. Elements in the same group have similarities, but their reactions and applications are not identical.
What the atomic number tells us
Calcium has atomic number 20. This is the number of protons in its nucleus. A neutral atom also has 20 electrons. Losing or gaining electrons makes an ion; it does not change the element unless the proton count changes.
The model's rings help count electrons by shell. They are not actual circular paths. A model of one atom and the properties of a whole material are different levels of description.
Temperature and state
25°C: Solid
Illustrative particle motion: sizes, distances and speeds are not to scale. Particles represent atoms or molecules.
← CoolHeat →
Melting point 841.85°C / Boiling point 1,483.85°C
Pure element at 1 atmosphere. Image conditions are explained in captions. Pictures do not change with temperature.