7) D

1 – chemical properties rely mainly on the number of electrons. Mass numbers are the sum of protons and neutron within an atom’s nucleus. Hence, changing the mass numbers would not change the chemical properties. Therefore, 1 is correct.

2 – An atom’s atomic number is the number of protons in the atom. Since the atomic number is 28, the atom will contain 28 protons. Therefore, 2 is correct.

3 – Mass number is equal to the number of protons + number of neutrons. An atom cannot have a mass number of 62 and have 62 neutrons. This would mean that it contains no protons which is incorrect.