How is the number of neutrons in the nucleus of an atom calculated?
o a) add the number of electrons and protons together.
ob) subtract the number of electrons from the number of protons,
oc) subtract the number of protons from the mass number.
od) add the mass number to the number of electrons.

C) Subtract the number of protons from mass number.

Explanation:

An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.

All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.

For example

The carbon have six protons and six neutrons so its atomic mass is 12 amu and atomic number is six.

Number of neutrons = mass number - number of protons

Number of neutrons =12 - 6

Number of neutrons = 6