Answer: Option (a) is the correct answer.
Explanation:
It is known that nucleus of an atom contains protons and neutrons whereas electrons revolve around the nucleus.
Also, it is known that protons have positive charge, neutrons are neutral and electrons have a negative charge. Therefore, electrons closer to the nucleus are attracted by the positive charge of protons.
Hence, as the number of shells increases in an atom according to their atomic number then the outer electrons move away from the nucleus and thus, they are weakly attracted by the nucleus.
Thus, we can conclude that the outer electrons are not as tightly bound as ones closer to the nucleus makes outer electrons of some substances able to be removed by friction.
