The speed of an electron in the orbit of the hydrogen atom in the ground state is

Correct answer: (c) c/137

Explanation

In Bohr's model the electron's speed in the nth orbit is vₙ = (Z/n) × c/137, where 1/137 is the fine-structure constant.

For hydrogen in the ground state (Z = 1, n = 1) that is c/137, about 2.2 × 10⁶ m/s.