Explanation:
In a neutral atom the number of protons equal the number of electrons. Also, it is known that atomic number means number of protons.
Atomic number of indium is 49 that means number of protons in indium is 49. Since it is a neutral atom so, number of electrons in an indium atom is also 49.
Whereas mass number means sum of total number of protons and neutrons.
Mass number = no. of protons + no. of neutrons
113 = 49 + no. of neutrons
no. of neutrons = 113 - 49
= 64
Hence, in a neutral indium atom no. of protons = no. of electrons = 49 and no. of neutrons is 64.
