Drawing Bohr Models of Atoms
Drawing Bohr
Models
Steps: First, remember APE MAN!!
A=P=E
Atomic number equals number of protons and electrons
M - A = N Mass number minus atomic number equals the number of neutrons
Next: put protons and neutrons in the nucleus, and electrons in the electron
shells.
1st energy shell holds up to 2
2nd energy shell holds up to 8
3rd energy shell holds up to 8
(but in high school, you'll learn that transition elements do weird things
with this rule! Forget about that for now and learn 2, 8, 8)
Now, let's get to drawing!
Look at Carbon.
Think about APE MAN.
Atomic number = protons = electrons, so ... the atomic number of Carbon is 6.... it must have
6 protons and 6 electrons.
Mass - atomic number = neutrons so.... the mass is 12, the atomic number is 6,
12-6 = 6 neutrons
IMPORTANT: round the mass number before subtracting!
Draw Carbon. Put the protons (6) and neutrons (6) in the nucleus, and electrons (6) in the
energy levels.
2 of them go in the first level, then 4 in the second level (which can hold up to 8 before it's
full.) Find out how many energy levels to draw by looking on Periodic table. What period is
Carbon in? The 2nd period, so it has 2 energy levels. See the two rings around the nucleus
below!! You can also write in the protons and neutrons like this: P6 N6 in the nucleus.
Now try drawing Boron, element number 5.
Do APE MAN for Boron. How many protons? neutrons? electrons?
Did you get 5 protons, 6 neutrons, and 5 electrons?
Did you round the mass before subtracting?
Draw Boron, putting the proper number of protons (5) and neutrons (6) and electrons (5) in
their proper places. Again find out how many energy levels to draw by looking at what period
it is in on the periodic table. It is in period 2!!!
Your drawing should look something like this. The protons, neutrons and electrons are all
represented correctly. Exactly how you drew them is not important as long as the numbers
and placement in nucleus and energy levels is correct!!
Good luck and keep practicing!!!