Why do electrons not fall into the nucleus even though they are attracted to protons in it? [Pg. No. 140]

Electrons are attracted towards the positively charged nucleus, but they do not fall into it because they exist only in certain fixed energy levels or shells around the nucleus. According to Bohr's model, an electron moving in a permitted shell does not lose energy continuously, so it does not spiral into the nucleus. It can lose or gain energy only when it jumps from one energy level to another. Thus, the concept of fixed energy levels helps explain the stability of atoms.