Explain how mass number is found with hydrogen atom with 3 neutrons, chlorine atom with 20 neutrons and nickel atom that has 30 neutrons.

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The mass number of an atom is determined by the number of protons and neutrons in its nucleus. Each proton contributes one unit in the mass number which is the same as the contribution made by a neutron.

To find the mass number of the isotopes given, we add the number of protons and neutrons. Hydrogen has one proton, if the hydrogen atom also has three neutrons the atomic mass number would be 4.

Similarly, chlorine has 17 protons; with 20 neutrons the mass number would be 17 + 20 which is equal to 37.

And finally nickel has 28 protons and with 30 neutrons which make the atomic mass number 58.

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