To solve this question, we need to know the atomic number of Ca, which is 20.
Atomic number = protons number = electrons number if the atom is neutral
Number of neutrons we calculate using the following formula:
A = p + n; where A = mass number; p = number of protons; n = number of neutrons.
For 40Ca:
Atomic number: 20
Number of protons: 20
Number of neutrons:
A = p + n
40 = 2 + n
n = 20
Number of electrons: 20
Mass number: 40
