1. Describe the composition of the nucleus in terms of protons and neutrons

A nucleus of an atom is made up of nucleons- protons and neutrons.

  1. Use the term atomic (proton) number Z.

The atomic number or proton number, denoted by Z, is the number of protons in an atom. The number of protons and number of electrons is always equal in a stable atom.

  1. Use the term mass (nucleon) number A.

The mass number of nucleon number, denoted by A, is the number of protons and neutrons in an atom. It is known as mass number, because protons and neutrons form an atom’s mass (the electrons have no mass).


The proton number, Z, is given on the bottom and the nucleon number, A, is given at the top.




Notes submitted by Lintha

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