Explanation:
Isotopes are defined as the species which have same number of neutrons but differ in the number of neutrons.
Fusion is defined as the nuclear reaction in which two smaller nuclei join together to form a heavier nuclei.
Atomic number is defined as the number of protons that are present in an element.
Fission is defined as the nuclear reaction in which a heavier nuclei splits into two or more smaller nuclei.
Atomic mass is defined as the sum of number of protons and neutrons that are present in an element.
From the above information:
For 1: The correct answer is isotopes.
For 2: The correct answer is atomic number.
For 3: The correct answer is atomic mass.
For 4: The correct answer is fission.
For 5: The correct answer is fusion.
