The atomic number of manganese is 25; its mass number is 55.
how many neutrons does an atom of manganese have in its nucleus?

a) 25 b) 80 c) 30 d) 55

c) 30

Explanation:

In an atom , the relation between the subatomic particles of the atom are given as follows -

For a neutral atom ,

Atomic number = number of protons = number of electrons ,

Mass number = number of protons + number of neutrons,

Hence , from the given information of the question,

Atomic number of Manganese = 25 ,

mass number of Manganese = 55 ,

Now, to calculate the number of neutrons , the above relation can be used -

Mass number = number of protons + number of neutrons,

Rearranging ,

number of neutrons = Mass number - number of protons

substituting the respective values ,

number of neutrons = 55 - 25 = 30 .