Barrons SAT Subject Test Chemistry, 13th Edition

Bohr Model of the Atom

In 1913, Niels Bohr (Denmark) proposed his model of the atom. This pictured the
atom as having a dense, positively charged nucleus and negatively charged
electrons in specific spherical orbits, also called energy levels or shells, around
this nucleus. These energy levels are arranged concentrically around the nucleus,
and each level is designated by a number: 1, 2, 3,... The closer to the nucleus,
the less energy an electron needs in one of these levels, but it has to gain energy to
go from one level to another that is farther away from the nucleus.
Because of its simplicity and general ability to explain chemical change, the
Bohr model still has some usefulness today.

TIP

Bohr’s electron distribution to principal energy levels has the formula 2n^2.

Principal Energy Level

Maximum Number of Electrons (2 n^2 )

1

2

2

8

3

18

4

32

5

50

Components of Atomic Structure

The chart below lists the basic particles of the atom and important information
about them.

When these components are used in the model, the protons and neutrons are