Exercise 8.6
Electrons move around the nucleus in orbits. Why do they not fly away from the atom? Explain what keeps them attracted to the nucleus.
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
They are held in by the electrostatic force of attraction between the negatively charged electron and the positively charged nucleus.
The nucleus contains protons, which carry positive charge; the electron carries negative charge. Unlike charges attract, so the electron is continuously pulled towards the centre.
That inward pull is what bends the electron's path into a closed orbit instead of letting it fly off in a straight line.
To actually escape the atom, an electron would have to be supplied with enough energy from outside to overcome this attraction.
The opposite worry — that the pull should make the electron fall into the nucleus — is answered by Bohr: in a stationary state the electron keeps a fixed amount of energy and loses none while moving.
With no energy lost, the electron neither escapes outward nor spirals inward. It stays in its shell, and can change only by absorbing or releasing a fixed amount of energy to jump to another shell.