The Bohr Model
The Bohr Model
In 1913, Niels Bohr began work on the Bohr
model of the atom
Bohr used Rutherford’s current idea of the
planetary model of the atom
Bohr realized that according to Rutherford’s
model, a planetary atom would have an
extremely short lifetime
Bohr used the emission spectrum of hydrogen to
create the Bohr model of the atom
The Bohr Model Principles1. Electrons assume only certain orbits
around the nucleus.
2. Each orbit has a different energy.
3. Light is emitted when an electron jumps
from a higher orbit to a lower orbit.
Light is absorbed when an electron jumps
from a lower to higher orbit.
4. The energy and frequency of light emitted
or absorbed is given by the difference
between the two orbit energies.
Drawing Bohr Models
Subatomic Particle Review
Proton – a positively charged particle
located in the nucleus of an atom
Neutron – a neutrally charged particle
located in the nucleus of an atom
Electron – a negatively charged particle
located in specific orbitals around the
nucleus
Subatomic Particle Review
Atomic Number = # Protons
Mass Number = # Protons + # Neutrons
# Neutrons = Mass # - Atomic Number
If neutral (no charge) –
# Protons = # Electrons
If # Protons > # Electrons –
Positive Charge
If # Protons < # Electrons –
Negative Charge
Bohr Models
1. Bohr models are used to predict reactivity in elements.
2. Reactivity refers to how likely an element is to form a compound with another element.
3. When looking at Bohr models, we look at its valence electrons (the electrons on the last energy level) to determine reactivity.
Drawing Bohr Models
1. Draw the nucleus.
2. Write the number of neutrons and the number of protons in the nucleus.
3. Draw the first energy level.
4. Draw the electrons in the energy levels according to the rules below. Make sure you draw the electrons in pairs.
5. Keep track of how many electrons are put in each level and the number of electrons left to use.
Rules for Energy Levels
1. Level 1 (closest to the nucleus) can hold
a maximum of 2e.
2. Level 2 can hold a max of 8e.
3. Level 3 can hold a max of 18e.
4. Level 4 can hold a max of 32e.
You must fill one level before going on to
draw the next level!
Guided Practice
In order to draw Bohr models of these elements, you must first determine the number of protons, neutrons, and electrons. Once you have found this information, follow the directions to draw your model.
6
C
Carbon
12.011
6 6 6
24
Protons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice16
S
Sulfur
32.066
Protons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model:
16 16 16
36
Guided PracticeProtons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model:
3
Li
Lithium
6.941
3 4 32
1
Guided PracticeProtons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model:
10
Ne
Neon
20.180
10 10 10
28
Guided PracticeProtons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model:
15
P
Phosphorus
30.974
15 16 15
35
Guided PracticeProtons: _____ Neutrons: _____ Electrons: ______
How many energy shells will this have? ____
How many valence (outer) electrons does this element have? ____
Bohr Model:
11
Na
Sodium
22.990
11 12 11
31