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 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 Carbon Atomic # = 6 Mass # = 12 Atomic mass = 12.011 amu

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

Bohr Diagrams Draw a larger circle around the nucleus circle to represent the first energy level for electrons Add more circles outside to include all of the energy levels you need for the atom. (Hint: In what period is the element?) Carbon Atomic # = 6 Mass # = 12 Atomic mass = 12.011 amu Carbon is in Period two and therefore needs two energy levels C 6p+ 6n0

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. Remember: Carbon Atomic # = 6 Mass # = 12 Atomic mass = 12.011 amu Energy Level # of e- 1 2 8 3 The number of electrons should be equal to the number of protons. C 6p+ 6n0 If you need a third level make your circles a little smaller.

Bohr Diagrams You now have a complete Bohr Diagram Carbon Atomic # = 6 Mass # = 12 Atomic mass = 12.011 amu C 6p+ 6n0

Electron Dot Diagrams 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 C The Elemental Symbol serves as the representation of the nucleus C

Electron Dot Diagrams C Dots are added around the nucleus to show electrons only in the outer energy level Like the Hund rule add 1 electron per side, then add more as needed. C Carbon has only 4 electrons in the 2nd energy level so we need only represent those 4

Electron Dot Diagrams C Lewis structures only apply to “Representative elements” (Group A elements) The maximum number of electrons that can be shown are 8 C Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

Electron Dot Diagrams O Lewis structures only apply to “Representative elements” (Group A elements) The maximum number of electrons that can be shown are 8 O Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

Electron Dot Diagrams Cl Lewis structures only apply to “Representative elements” (Group A elements) The maximum number of electrons that can be shown are 8 Cl Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

Electron Dot Diagrams Li Lewis structures only apply to “Representative elements” (Group A elements) The maximum number of electrons that can be shown are 8 Li Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.

Electron Dot Diagrams Fe Cu Ag Pb Transition metals don’t have valence electrons. They have Oxidation Numbers +2 +2 +2 +4 Fe Cu Ag Pb We’ll Talk about Oxidation Numbers Next Week!