1. Drawing Atoms

2. Draw a Bohr model of an atom Describe the meaning of the energy level number Key Words Bohr model energy level valence electrons

3. Bohr model - electrons occupy special positions called orbits or energy levels around the nucleus. It is some times called the "planetary model"

4. 1 st – holds two electrons (e - ) 2 nd – holds eight e - 3 rd – holds eight e - Electrons occupy the closest orbital first. e - in the outer orbit are VALENCE electrons. Determine how an element will chemically react.

5. Drawing a Complete Bohr Atom 1.Determine the number of n o, p +, e - in the atom. 2.Draw the nucleus. 3.Label the #of protons and neutrons in the nucleus 4.Add orbits and fill with the appropriate # of e -. 7p + 7n o Nitrogen (N) p + : 7 n o : 14 – 7 = 7 e - : 7

6. Atoms are identified by the number of protons in the nucleus. Must indicate protons (9p + ) in the nucleus. Fluorine 9 p + 10 n o 9 e - 9p + 10n o

7. Another way of drawing the Bohr Model Usually for bigger atoms... Only the last orbit is drawn with the electrons. 11p + 12n o Sodium (Na) 11p + 2e 8e

8. Draw new Bohr atoms for all elements across Period 3. Starting with Sodium…

10. Did we notice any trends or patterns? Elements with the same number of valence electrons are in the same column (group). As you move across (period) the Periodic Table, the number of valence electrons increases. The last group of elements have a full last orbit. (8 electrons)