the bohr model -...

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