Vocabulary

• Bohr model• Energy level (shell)• Valence electrons

Bohr Model• Electrons orbit the nucleus

of an atom in set energy levels

P = 20N = 20

Energy Level

• The specific energies an electron in an atom can have

• In the Bohr model used to describe the different orbits or shells that the electrons travel in around the nucleus

Valence Electrons• The electrons in the highest or

outermost energy level

Bohr Models are NOT Boring!

How to Draw Bohr Diagrams

Bohr models-a simple way to draw an atom

• Bohr models are a way of showing the electrons in an atom.

• Electrons are arranged in energy levels. In actual atoms, those energy levels are clouds of crazy shapes where the electrons are likely to be found.

• Bohr models show the electron energy levels in nice, neat, easy to draw circles.

Bohr Diagrams

1) Find the element on the periodic table.2)Determine the number of electrons--it is the

same as the atomic number.3)This is how many electrons you will draw.

Bohr Diagrams• Find out which period

(row) your element is in.

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•Elements in the 1st period have one energy level.•Elements in the 2nd period have two energy levels, and so on.

1

2

3

4

5

6

7

The electron energy levels or shells surrounding the nucleus each hold a particular number of electrons.

Energy levels or shells are represented by n= period number:

n=1 max 2 electronsn=2 max 8 electronsn=3 max 18 electronsn=4 max 32 electrons

Remember: The outer shell of an atom (no matter what letter) can only hold 8 electrons!

Max Electrons in each Energy Levels2 electrons in 1st, 8 electrons in 2nd, 18 electrons in the 3rd, 32 electrons in the 4th

P =

N =

2 e

Things get a little crazy in the 3rd and 4th rings…8 go into the 3rd, then the next 2 go into the 4th, then the electrons go back and fill up the 3rd

8 e

18 e

32 e

Max rule (2,8,18,32)

Fill rule (2,8,8,2 then rest in 3rd)

Bohr Diagrams1) Draw a nucleus.

2)Write the number of Protons and Neutrons the element has inside the nucleus.

P = 6

N = 6

Note: Round mass to nearest 1 when figuring neutrons.

Bohr Diagrams

1) Carbon is in the 2nd period, so it has two energy levels, or shells.

2) Draw the shells around the nucleus.

P = 6

N = 6

Bohr Diagrams1) Add the electrons.

P= 6

N = 6

2) Carbon has 6 electrons.3) The first shell can only

hold 2 electrons.4) The second shell put the

remaining 4 electrons

Bohr Diagrams

Try Hydrogen:Atomic Mass:Atomic Number:Protons:Electrons:Neutrons:Shells:Valence electrons:

HP+ =

N0 =

Bohr Diagrams

Try Hydrogen:Atomic Mass: 1.008Atomic Number: 1Protons: 1Electrons: 1Neutrons: 0Shells: 1Valence electrons: 1

HP = 1

N = 0

Bohr Diagrams

P= 1

N= 0

Check Yourself.

H (1)

Bohr Diagrams

Try Helium

HeP=

N=

Try Helium:Atomic Mass:Atomic Number:Protons:Electrons:Neutrons:Shells:Valence electrons:

Bohr Diagrams

Try Helium

HeP= 2

N= 2

Try Helium:Atomic Mass: 4.003Atomic Number: 2Protons: 2Electrons: 2Neutrons: 2Shells: 1Valence electrons: 2

Bohr Diagrams

P= 2

N= 2

Check Yourself!

He (2)

Bohr Diagrams

OP+=

N0=

Try Oxygen:Atomic Mass:Atomic Number:Protons:Electrons:Neutrons:Shells:Valence electrons:

Bohr Diagrams

P= 8

N= 8

Try Oxygen:Atomic Mass: 15.999Atomic Number: 8Protons: 8Electrons: 8Neutrons: 8Shells: 2Valence electrons: 6

Bohr Diagrams

P= 8

N= 8

Check Yourslef!

O (2,6)

Bohr Diagrams

P= 13

N= 14

Try Aluminum:Atomic Mass: 26.982Atomic Number: 13Protons:13Electrons:13Neutrons:14Shells:3Valence electrons:3

Bohr Diagrams

Check Yourself!

Al (2,8,3)P= 13

N= 14

Bohr Diagrams

P= 13

N= 14

Try Aluminum:Atomic Mass: 26.982Atomic Number: 13Protons:13Electrons:13Neutrons:14Shells:3Valence electrons:3

Bohr Diagrams

P= 22

N= 26

Try Titanium (Ti) :Atomic Mass: 47.88Atomic Number: 22Protons: 22Electrons: 22Neutrons: 26Shells: 4Valence electrons: 2

Bohr Diagrams

Check Yourself!

Ti (2,8,10,2)P= 22

N= 26