Answer:
Step-by-step explanation:
The number of protons and neutrons in an ion is same as that of the parent atom. The difference only occurs in the number of electrons as ions are formed due to loss or gain of electrons.
The number of positive charges of an atom is equivalent to the number of protons it contains.
The mass of the atom is the collective number of protons and neutrons in the nucleus of the atom. (Electrons have negligible mass in comparison to the mass of the nucleus).
Atomic number= number of protons= number of positive charges = Z
Mass number= number of protons and neutrons= N
Number of electons= number of protons = Z (if an atom is electrically neutral)
Number of electons = Z - charge on the atom (in case of ions)
Calcium atom contains Z=20 and N=40.
Number of protons = number of electrons = Z = 20
Number of neutrons = A-Z = 20
In case of Ca2+ ion,
Number of protons = Z = 20
Number of neutrons = A-Z = 20
Number of electrons = Z-(charge on ion=2) = 20–2 = 18