What is the atomic number of Calcium?

The answer

The atomic number of Calcium is 20.

The periodic table

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Calcium (Ca) is atomic number 20 in the periodic table.

Why

The atomic number tells you how many protons are in the nucleus (center) of one atom of Calcium. For Calcium, there are 20 protons. This number is what makes Calcium different from every other element.

Remember it

Calcium = 20 protons = atomic number 20.

Quick recap

Calcium has atomic number 20.
Atomic number means number of protons.
Every Calcium atom has 20 protons in its nucleus.

Read it in the NCERT book

Atomic Number · Class 9

Ask next

What is the symbol for Calcium? How many electrons does a neutral Calcium atom have? Where is Calcium used in daily life?

Written by the LLOS.ai tutor, checked against NCERT chapters. Asked by Pawan N. from New Delhi, India on 26 Oct 2026, 8:57 PM IST