1. Atomic Structure

4. Key 11 Na Sodium 22.99 Atomic Number Element symbol Element name Average atomic mass*

5. Key 11 Na Sodium 22.99 Atomic Number Number of Protons Number of Electrons (when atom is neutrally charged) Property unique to each element

6. Key 11 Na Sodium 22.99 Element symbol Sometimes abbreviation of English name Sometimes abbreviation of Latin/Greek name Familiarize yourself with them and Chemistry problems will become easier

7. Key 11 Na Sodium 22.99 Element name What we call it

8. Key Average atomic mass* Weighted Average number of Protons and Neutrons (approximately) Na Sodium 22.99 11

9. Subatomic Particles the particles that make up an atom Protons – high mass, positive charge. Found in nucleus. Neutrons – high mass, no charge. Found in nucleus. Electrons – low mass, negative charge. Found orbiting around nucleus. (abbreviated e – )

10. Basic Electrical Charge Laws + and – : Attract (pull together) – and – : Repel (push away) + and + : Repel (push away) Like charges repel and Opposites attract

11. An Atom Nucleus 1 proton = H = hydrogen

12. Why doesn’t the electron fall into the nucleus? It orbits because the electron is moving really fast around the nucleus. Because the electron has such a low mass, even a small amount of energy makes it move very fast.

13. An Atom Nucleus 1 proton = H = hydrogen

14. Another Atom Size of atom Size of nucleus 2 protons = He = helium

15. Zooming Out – Another Atom 3 protons = Li = lithium

16. Yet Another Atom 4 protons = Be = beryllium

17. 5 protons = B = boron

18. 6 protons = C = carbon

19. Valence Electrons valence electrons – the outermost electrons. (only the electrons in the last s and p orbitals). Only the electrons in the outermost energy levels are available for bonding.

20. Valence Electrons How many electrons in the valence shell of a carbon atom?

21. 6 protons = C = carbon Inner electrons = 2 e – not available for bonding Outer electrons = 4 e – available for bonding

22. 4 electrons in valence shell

23. How many e – in valence shell?

31. Lewis Dot Structures Lewis dot structures are a convenient way to show how many valence electrons an atom has. Example: Draw the Lewis dot structure for hydrogen. H

32. Lewis Dot Structures  Write the symbol for the element.  Look for the “A” number at the top of the element’s column (e.g. 5A). This is the number of valence electrons.  Draw that many dots around the symbol. Draw at most 2 dots on each side (top, bottom, left, right)  The maximum number of dots is 8.  Exception: Helium only has 2 dots. He Ne

33. More Lewis Structure Practice  Draw the Lewis structure for oxygen.  Draw the Lewis structure for magnesium.  Draw the Lewis structure for chlorine. O Mg Cl

34. Even More Lewis Structure Practice  Draw the Lewis structure for carbon.  Draw the Lewis structure for potassium.  Draw the Lewis structure for phosphorus. C K P

35. Ne F ONC B Be He Li H KrAr Cl Br Xe ISPSi Mg Al Ca Na K

36. 4 e – in valence shell

37. Valence Shell Only the electrons in the outermost energy levels are available for bonding. valence shell – the outermost bundle of energy levels.