What does Bohr's model of the atom look like?

1 Answer
Jul 19, 2014

The Bohr model consists of negatively-charged electrons moving in orbits about a small, positively-charged nucleus.


It is often called a "planetary" model, because it looks like the Sun with the electrons revolving around it like planets in their orbits.

Planetary Model
(from www.thephysicsmill.com)

The orbits correspond to energy levels or shells. The energy of each shell increases as it gets further away from the nucleus.

As the atomic number of the atom increases, the number of electrons orbiting the nucleus also increases.

The electrons fill the inner shells first, because they are of lower energy than the outer shells.

The first inner shell (known as the K shell) can hold two electrons. The next shell (the L shell) can hold eight electrons.

Thus, hydrogen (atomic number 1) has one electron in the K shell. Helium has two electrons in the K shell.

Lithium has2 K electrons and 1 L electron. Beryllium has 2 K electrons and 2 L electrons, Boron has 2 K electrons and 3 L electrons, etc.

The video below shows how Bohr came up with the planetary model and shows how the model explains the line spectra of elements.