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Periodic table · chemistry · physics
Element story

Calcium

Atomic number 20 means that every Calcium nucleus contains 20 protons. That proton count is the element's identity: change it and you no longer have Calcium.

Start with the nucleus

Atomic number 20 means that every Calcium nucleus contains 20 protons. That proton count is the element's identity: change it and you no longer have Calcium.

Calcium (Ca) is chemical element 20. It belongs to the alkaline-earth metals, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.

In practice, it turns up most often in bones and teeth, cement and lime and biology.

See the atom

Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.

What this number means

Atomic number 20 means that every Calcium nucleus contains 20 protons. That proton count is the element's identity: change it and you no longer have Calcium.

Keep exploring

→ Calcium · Atomic structure · Periodic trends

20CaCalcium
Calcium · Ca · Z = 20

Calcium (Ca) is chemical element 20. It belongs to the alkaline-earth metals, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.

Understanding the element

Calcium (Ca) is chemical element 20. It belongs to the alkaline-earth metals, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.

Where do we encounter it?

In practice, it turns up most often in bones and teeth, cement and lime and biology.

What its position in the table tells us

Calcium sits in period 4, group 2 and the S block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.