5. Calcium-40 and Calcium-42 both share the same number of protons
number of neutrons
number of electrons
mass number

The answer options is d

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom