Question

How many protons, neutrons, and electrons does a magnesium atom with a mass number of 25 contain?

Answer 1

Magnesium (Mg) has atomic number of $$12$$ and mass number-25.
We know that for a neutral atom-
Atomic number (Z) = no. of proton = no. of electron
No. of neutron = Mass number(Z) - Atomic number (A)

For Mg,
No. of proton = no. of electron =12
No. of neutron = Mass number(Z) - Atomic number (A) = 25-12 =13