◦ Name Color Burned 1 2 3 4 5 6 Unknown #1 Unknown #2

Today’s Lab

Modeling and Representing Atoms on Paper

How to draw Bohr Diagrams and Electron Dot Diagrams (sometimes called Lewis

Structures)

Pictographic representation of an Atom Shows information about the nucleus Electron energy levels Good for index cards and flash cards

Bohr Diagrams

Start with a rectangle about 2” x 4”

Bohr Diagrams

At the top write the name, Atomic number, Mass number of the element and the atomic mass

Bohr Diagrams

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amu

Draw a small circle below the text that will represent the nucleus of the atom

Bohr Diagrams

In the circle write: the elemental symbol the number of Protons the number of Neutrons

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amu

C 6p+

6n0

Draw a larger circle around the nucleus circle to represent the first energy level for electrons

Bohr Diagrams

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amu

Add more circles outside to include all of the energy levels you need for the atom.

(Hint: In what period is the element?)

Carbon is in Period two and therefore needs two energy levels

C 6p+

6n0

Find out which period (row) your element is in.

Elements in the 1st period have one energy level.

Elements in the 2nd period have two energy levels, and so on.

Bohr Diagrams

Now add electrons, as small dots, to each energy level as allowed until you have the proper number of electrons for a neutral element.

Bohr Diagrams

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amuThe number of electrons should be equal to the number of protons.

Remember:Energy Level

# of e-

1 22 83 8

C 6p+

6n0

If you need a third level make your circles a little smaller.

You now have a complete Bohr Diagram

Bohr Diagrams

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amu

C 6p+

6n0

1) Draw a nucleus with the element symbol inside.

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

3) Draw the shells around the nucleus.

Bohr Diagrams

C

1) Add the electrons.2) Carbon has 6

electrons.3) The first shell can

only hold 2 electrons.

Bohr Diagrams

C

1) Since you have 2 electrons already drawn, you need to add 4 more.

2) These go in the 2nd shell.

3) Add one at a time -starting on the right side and going counter clock-wise.

Bohr Diagrams

C

1) Check your work.2) You should have 6

total electrons for Carbon.

3) Only two electrons can fit in the 1st shell.

4) The 2nd shell can hold up to 8 electrons.

5) The 3rd shell can hold 18, but the elements in the first few periods only use 8 electrons.

Bohr Diagrams

C

Try the following elements on your own:

a) Hb) Hec) Od) Ale) Nef) K

Bohr Diagrams

C

Try the following elements on your own:

a) H – 1 electronb) Hec) Od) Ale) Nef) K

Bohr Diagrams

H

Try the following elements on your own:

a) Hb) He - 2 electronsc) Od) Ale) Nef) K

Bohr Diagrams

He

Try the following elements on your own:

a) Hb) Hec) O - 8 electronsd) Ale) Nef) K

Bohr Diagrams

O

Try the following elements on your own:

a) Hb) Hec) Od) Al - 13 electronse) Nef) K

Bohr Diagrams

Al

Try the following elements on your own:

a) Hb) Hec) Od) Ale) Ne - 10 electronsf) K

Bohr Diagrams

Ne

Try the following elements on your own:

a) Hb) Hec) Od) Ale) Nef) K - 19 electrons

Bohr Diagrams

K

Also called Lewis Structures Representation of valence electrons only Useful only for “Representative elements” Gives some indication of the geometry

(shape) of compounds when used for bonding diagrams

Easy to draw

Electron Dot Diagrams

To find the # of valence electrons look at the group

Group 1 Group 2 Group # = # of valence electrons

Valence Electrons

The Elemental Symbol serves as the representation of the nucleus

Electron Dot Diagrams

Dots are added around the nucleus to show electrons only in the outer energy level

Electron Dot Diagrams

Carbon has only 4 electrons in the 2nd energy level so we need only represent those 4

Like the Hund rule add 1 electron per side, then add more as needed.

Lewis structures only apply to “Representative elements” (Group A elements)

Electron Dot Diagrams

Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

The maximum number of electrons that can be shown are 8

Lewis structures only apply to “Representative elements” (Group A elements)

Electron Dot Diagrams

The maximum number of electrons that can be shown are 8

Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

Lewis structures only apply to “Representative elements” (Group A elements)

Electron Dot Diagrams

The maximum number of electrons that can be shown are 8

Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

Lewis structures only apply to “Representative elements” (Group A elements)

Electron Dot Diagrams

The maximum number of electrons that can be shown are 8

Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

Transition metals don’t have valence electrons. They have Oxidation Numbers

Electron Dot Diagrams

+2 +2 +2 +4

We’ll Talk about Oxidation Numbers Next Week!