Isotopes are forms of an element that have the same number of protons but different numbers of neutrons. There are three isotopes of hydrogen: hydrogen, deuterium (hydrogen-2) and tritium ...

The typical size of atoms and small molecules is around 1 × 10-10 m (0.1 nm). For example: diameter of a hydrogen atom, H 1.0 × 10-10 m width of a hydrogen molecule, H 2 2.9 × 10-10 m ...

Postulates for Bohr’s model are: 1. Electron in hydrogen atom moves around the nucleus in circular path of fixed radius and energy. These paths are called orbits or energy levels. 2.