For a hydrogen atom, H, the one electron goes into the first energy
level.
Draw a circle and label it with the symbol of the nucleus, H.
Write the number of protons for the nucleus, 1p+.
Draw an arc to represent the first energy level. Label the arc
1e- to represent that there is one electron in this energy
level.
For a helium atom, He, the two electrons go into the first energy
level.
Draw a circle and label it with the symbol of the nucleus, He.
Write the number of protons for the nucleus, 2p+.
Draw an arc to represent the first energy level. Label the arc
2e- to represent that both electrons reside in this energy
level.
For a lithium atom, Li, two of the three electrons go into the first
energy level. The third electron goes into the second energy level. This electron
in the outer energy level is called the valence
electron. The two electrons in the first energy level are called the core
electrons.
Draw a circle and label it with the symbol of the nucleus, Li.
Write the number of protons for the nucleus, 3p+.
Draw an arc to represent the first energy level. Label the arc
2e- to represent that 2 of the 3 electrons reside in
this energy level.
Draw a second arc to represent the second energy level. Label
the arc 1e- to represent that the 3rd electron resides
in this outer energy level.
Let's see if you've grasp the idea. You should
be able to draw Bohr diagrams for the first 20 elements of the periodic table.
Click here
to check your diagrams.
Section
4.6 Arrangement
of Electrons
in Principal
Energy
Levels ..p87
