Solution:concept - Calcium is metal that belongs to group 2 and period 4. It belongs to alkaline earth metals.
The atomic number (Z) of silver is 20, so it follows from the relationship that the number of protons inside the nucleus and the number of electrons outside the nucleus in the orbital of the calcium atom are both equal to 20.
Following is a description of the relationship between atomic mass, protons, and neutrons:
Atomic mass (A) = No. of protons + No. of neutrons
It is well known that calcium has an atomic mass of 40.
Additionally, we know that calcium has 20 protons.
Neutron number, therefore, equals atomic mass (A) - proton number.
Neutron count is 40-20=20.
There are 20 neutrons in calcium.
Hence, option 1 is correct.