# Bohr Model Practice ```Name:___________________________Period:___
Bohr Model Notes
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The atomic number is the number of protons in an atom of each element.
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In a neutral atom, the number of protons is equal to the number of electrons.
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Bohr Models are used to show arrangement of electrons in energy levels (shells).
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Electrons are placed in the lowest shell first (closest to the nucleus).
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Once the first shell is full, additional electrons are placed in the next shell, and so on.
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Each period (row) on the periodic table begins and ends a new energy level.
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For the first three periods on the periodic table, the maximum number of electrons in each shell is:
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1st:
–
2nd: 8 electrons
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3rd: 8 electrons
2 electrons
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(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.)
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Bohr Model Practice – Use your periodic table.
– Fill in the blanks below.
• Phosphorus
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Symbol: _________
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Atomic Number: _________
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Atomic Mass: _________
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Protons: _________
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Neutrons: _________
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Electrons: _________
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Write the number of protons (___p+) in the center.
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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
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