Modeling and Modeling and Representing Atoms on Representing Atoms on

PaperPaper

How to draw Bohr Diagrams How to draw Bohr Diagrams and Electron Dot Diagrams and Electron Dot Diagrams

(sometimes called Lewis (sometimes called Lewis Structures)Structures)

Bohr DiagramsBohr Diagrams

Pictographic representation of an Pictographic representation of an AtomAtom

Shows information about the nucleusShows information about the nucleus

Electron energy levelsElectron energy levels

Good for index cards and flash cardsGood for index cards and flash cards

Start with a rectangle about 2” x 4”Start with a rectangle about 2” x 4”

Bohr DiagramsBohr Diagrams

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

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amu

Bohr DiagramsBohr Diagrams

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

In the circle write:In the circle write: the elemental the elemental symbolsymbol the number of the number of ProtonsProtons the number of the number of NeutronsNeutrons

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amu

C 6p+

6n0

Bohr DiagramsBohr Diagrams

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

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amu

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

(Hint: In what (Hint: In what period is the period is the element?)element?)

Carbon is in Period two and therefore needs two energy levels

C 6p+

6n0

Bohr DiagramsBohr Diagrams

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

Carbon Atomic # = 6 Mass # = 12

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

Remember:

EnergEnergy y

LevelLevel

# of # of ee--

11 22

22 88

33 88C 6p+

6n0

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

Bohr DiagramsBohr Diagrams

You now have a complete Bohr You now have a complete Bohr DiagramDiagram

Carbon Atomic # = 6 Mass # = 12

Atomic mass = 12.011 amu

C 6p+

6n0

Bohr DiagramsBohr Diagrams

Electron Dot DiagramsElectron Dot Diagrams

• Also called Lewis StructuresAlso called Lewis Structures

• Representation of valence electrons onlyRepresentation of valence electrons only

• Useful only for “Representative Useful only for “Representative elements”elements”

• Gives some indication of the geometry Gives some indication of the geometry (shape) of compounds when used for (shape) of compounds when used for bonding diagramsbonding diagrams

• Easy to drawEasy to draw

Electron Dot DiagramsElectron Dot Diagrams

• The Elemental Symbol serves as the The Elemental Symbol serves as the representation of the nucleusrepresentation of the nucleus

Electron Dot DiagramsElectron Dot Diagrams

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

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.

Electron Dot DiagramsElectron Dot Diagrams

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

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

Electron Dot DiagramsElectron Dot Diagrams

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

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.

Electron Dot DiagramsElectron Dot Diagrams

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

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.

Electron Dot DiagramsElectron Dot Diagrams

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

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.

Electron Dot DiagramsElectron Dot Diagrams

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

+2 +2 +2 +4

We’ll Talk about Oxidation Numbers Next Week!