2. HELIUM ATOM + N N + - - proton electron neutron Shell What do these particles consist of?

3. ATOMIC STRUCTURE Particle proton neutron electron Charge + ve charge -ve charge No charge 1 1 nil Mass

4. ATOMIC STRUCTURE the number of protons in an atom the number of protons and neutrons in an atom He 2 4 Atomic mass Atomic number number of electrons = number of protons

5. ATOMIC STRUCTURE Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. first shella maximum of 2 electrons second shella maximum of 8 electrons third shella maximum of 8 electrons

6. ATOMIC STRUCTURE Three ways to represent the atomic structure of an element or compound; 1.Lewis Notation 2.Rutherford-Bohr Model 3.The Ball and Stick Model

7. Determine the number of shells and the number of valence electrons for:

14. Helium is the exception in Group 8. Since it has just one shell, that shell can only fit 2 electrons instead of 8. It is in this group because all the elements have a full outer shell.

15. Lewis Electron Dot Diagrams Invented by the American chemist, G.N. Lewis. 1.Write the chemical symbol 2.Write the appropriate number of dots in a clockwise manner

16. Lewis Structures 1)Write the element symbol. 2)Carbon is in the 4 th group, so it has 4 valence electrons. 3)Starting at the right, draw 4 electrons, or dots, counter- clockwise around the element symbol.

17. Lewis Structures 1)Check your work. 2)Using your periodic table, check that Carbon is in the 4 th group. 3)You should have 4 total electrons, or dots, drawn in for Carbon.

18. Lewis Structures a)H b)P c)Ca d)Ar e)Cl f)Al

19. Lewis Structures a)H b)P c)Ca d)Ar e)Cl f)Al

20. Lewis Structures On your worksheet, try these elements on your own: a)H b)P c)Ca d)Ar e)Cl f)Al

21. Lewis Structures a)H b)P c)Ca d)Ar e)Cl f)Al

22. Lewis Structures a)H b)P c)Ca d)Ar e)Cl f)Al

23. Lewis Structures a)H b)P c)Ca d)Ar e)Cl f)Al

24. Lewis Structures a)H b)P c)Ca d)Ar e)Cl f)Al

25. BOHR-RUTHERFORD DIAGRAMS Bohr-Rutherford diagrams should be drawn using the following steps:  Draw the nucleus with the proper number of protons (+1) and neutrons (0).  Draw the first electron shell with the appropriate number of electrons (-1).

26. BOHR-RUTHERFORD DIAGRAMS  Draw the second valence shell (if applicable) with the appropriate number of electrons (-1).  Continue to draw valence shells with electrons until you have the proper number of electrons for the element.

27. Example: sulfur

28. EXAMPLES Draw the Bohr- Rutherford Diagram for: Mg & Ca

29. Magnesium (Mg) and calcium (Ca)