Answer:
d, 34 neutrons
Explanation:
Mass number is the sum of the number of protons and the number of neutrons.
Atomic number equals to the number of protons.
Since the element has an atomic number of 31, it has 31 protons. The number of neutrons equal to mass number - no. of protons,
which in this case is 65 - 31
= 34 neutrons.
In a neutral atom, the no. of electrons equal to the no. of protons, because each proton carries a +1 charge and each electron carries a -1 charge. To cancel out the charge, their numbers must be equal. So, this atom has 31 electrons.
From the options, only d is correct. (34 neutrons)
