Modeling and Representing Atoms on Paper How to draw Bohr Diagrams and Electron Dot Diagrams (sometimes called Lewis Structures)

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

Start with a rectangle about 2” x 4” 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 At the top write the name, Atomic number, Mass number of the element and the atomic mass Carbon Atomic # = 6 Mass # = 12 Atomic mass = amu Bohr Diagrams

Draw a small circle below the text that will represent the nucleus of the atom Draw a small circle below the text that will represent the nucleus of the atom In the circle write: In the circle write: the elemental symbol the elemental symbol the number of Protons the number of Protons the number of Neutrons the number of Neutrons Carbon Atomic # = 6 Mass # = 12 Atomic mass = amu C 6p + 6n 0 Bohr Diagrams

Draw a larger circle around the nucleus circle to represent the first energy level for electrons Draw a larger circle around the nucleus circle to represent the first energy level for electrons Carbon Atomic # = 6 Mass # = 12 Atomic mass = 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 + 6n 0 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. Now add electrons, as small dots, to each energy level as allowed until you have the proper number of electrons for a neutral element. Carbon Atomic # = 6 Mass # = 12 Atomic mass = amu The number of electrons should be equal to the number of protons. Remember: Energ y Level # of e C 6p + 6n 0 If you need a third level make your circles a little smaller. Bohr Diagrams

You now have a complete Bohr Diagram You now have a complete Bohr Diagram Carbon Atomic # = 6 Mass # = 12 Atomic mass = amu C 6p + 6n 0 Bohr Diagrams

Electron Dot Diagrams Also called Lewis Structures Also called Lewis Structures Representation of valence electrons only Representation of valence electrons only Useful only for “Representative elements” Useful only for “Representative elements” Gives some indication of the geometry (shape) of compounds when used for bonding diagrams Gives some indication of the geometry (shape) of compounds when used for bonding diagrams Easy to draw Easy to draw

Electron Dot Diagrams The Elemental Symbol serves as the representation of the nucleus 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 Dots are added around the nucleus to show electrons only in the outer energy level Carbon has only 4 electrons in the 2 nd 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 Diagrams Lewis structures only apply to “Representative elements” (Group A elements) Lewis structures only apply to “Representative elements” (Group A 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 Diagrams Lewis structures only apply to “Representative elements” (Group A elements) Lewis structures only apply to “Representative elements” (Group A 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 Diagrams Lewis structures only apply to “Representative elements” (Group A elements) Lewis structures only apply to “Representative elements” (Group A 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 Diagrams Lewis structures only apply to “Representative elements” (Group A elements) Lewis structures only apply to “Representative elements” (Group A 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 Diagrams Transition metals don’t have valence electrons. They have Oxidation Numbers Transition metals don’t have valence electrons. They have Oxidation Numbers We’ll Talk about Oxidation Numbers Next Week!