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Atomic Number and Mass Number

Atomic number is the number of protons present in the atom of an element.
It is represented by the letter Z.
Atomic number
= Number of protons
= Number of electrons
Each element has a unique atomic number.
For example, an atom of sodium has 11 protons. Therefore, the atomic number of sodium is 11.
Mass number is the total number of protons and neutrons present in the nucleus of an atom.
It is denoted by the symbol A.
Mass number = Number of protons + Number of neutrons
For example, an atom of carbon has 6 protons and 6 neutrons. Thus, the mass number of carbon is 12.
An atom of an element is represented as AZ X, where A indicates the mass number and Z indicates the atomic number.
Number of neutrons
= Mass number − Atomic number

A − Z

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