Name:___________________________Period:___
Bohr Model Notes
•
The atomic number is the number of protons in an atom of each element.
•
In a neutral atom, the number of protons is equal to the number of electrons.
•
Bohr Models are used to show arrangement of electrons in energy levels (shells).
•
Electrons are placed in the lowest shell first (closest to the nucleus).
•
Once the first shell is full, additional electrons are placed in the next shell, and so on.
•
Each period (row) on the periodic table begins and ends a new energy level.
•
For the first three periods on the periodic table, the maximum number of electrons in each shell is:
–
1st:
–
2nd: 8 electrons
–
3rd: 8 electrons
2 electrons
•
(Beginning with the 4th period transition metals, the order of filling shells adds a new twist which
will be taught with a newer model which uses sublevels and orbitals.)
•
Bohr Model Practice – Use your periodic table.
– Fill in the blanks below.
• Phosphorus
•
Symbol: _________
•
Atomic Number: _________
•
Atomic Mass: _________
•
Protons: _________
•
Neutrons: _________
•
Electrons: _________
•
Write the number of protons (___p+) in the center.
•
•
Add electrons. Start with the 1st shell. Place 1 e- on the right and 1 e- left side of the shell.
Add electrons 1 at a time starting on the right, then top, left, and bottom. Then pair them going
around again counter-clockwise, starting on the right.
1
Bohr Model Worksheet
Use the description sheet and the periodic table to help you complete the following Bohr
models.
1. How many electrons can each shell hold?
a. 1st = _________
b. 2nd = _________
c. 3rd = _________
Element
Atomic Atomic
Protons Neutrons Electrons
#
Mass
Carbon
6
12
Hydrogen
1
1
Lithium
3
Magnesium
12
24
Boron
5
11
6
6
3
6
3
2
Bohr Model