Modeling and Representing Atoms on Paper

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

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

3. Bohr Diagrams • Start with a rectangle about 2” x 4”

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

5. 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

6. 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

7. 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 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.

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

9. 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

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

11. Electron Dot Diagrams • 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

12. Electron Dot Diagrams • 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.

13. Electron Dot Diagrams • 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.

14. Electron Dot Diagrams • 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.

15. Electron Dot Diagrams • 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.

16. Electron Dot Diagrams • 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!