1. The Why and How of Ions
Featuring the Return of Bohr-Rutherford Diagrams and the Periodic Table

2. Bohr-Rutherford Diagrams
Bohr-Rutherford diagrams (or simply Bohr diagrams) are used to show the arrangement of electrons in the atom, e.g.:

3. How To Draw Bohr Diagrams
Find your element on the periodic table.
Determine the number of electrons, which for a neutral atom is equal to the number of ?

4. How To Draw Bohr Diagrams
Find your element on the periodic table.
Determine the number of electrons, which for a neutral atom is equal to the number of protons, which is equal to the ?

5. How To Draw Bohr Diagrams
Find your element on the periodic table.
Determine the number of electrons, which for a neutral atom is equal to the number of protons, which is equal to the atomic number.

6. How To Draw Bohr Diagrams
3) Determine which period (row) your element is in.
Elements in the 1st period have one energy level or shell.
Elements in the 2nd period have two, and so on.

7. How To Draw Bohr Diagrams
4) Draw a nucleus with the element symbol (and optionally, the #s of protons and neutrons) inside.
5) Draw the shells around the nucleus.
Carbon is in the 2nd period, so it has two energy levels or shells. C

8. How To Draw Bohr Diagrams
6) Add the electrons.
Carbon has 6 electrons.
The first shell can only hold ? C

9. How To Draw Bohr Diagrams
6) Add the electrons.
Carbon has 6 electrons.
The first shell can only hold 2 electrons. C

10. How To Draw Bohr Diagrams
You need to add 4 more so these go in the 2nd shell.
The 2nd shell can hold up to ? C

11. How To Draw Bohr Diagrams
You need to add 4 more so these go in the 2nd shell.
The 2nd shell can hold up to 8 electrons; the 3rd shell can hold 18, but the elements in the first few periods only use 8 electrons. C

12. How To Draw Bohr Diagrams
7) Check your work: Count your electrons per shell and your total electrons! C

13. Bohr Diagrams: Practice
Try drawing Bohr diagram for each of the following elements on your own: H He O Al Ne K C

14. Bohr Diagrams: Practice
Try drawing Bohr diagram for each of the following elements on your own:
H – 1 electron He O Al Ne K H

15. Bohr Diagrams: Practice
Try drawing Bohr diagram for each of the following elements on your own: H
He - 2 electrons O Al Ne K He

16. Bohr Diagrams: Practice
Try drawing Bohr diagram for each of the following elements on your own: H He
O - 8 electrons Al Ne K O

17. Bohr Diagrams: Practice
Try drawing Bohr diagram for each of the following elements on your own: H He O
Al - 13 electrons Ne K Al

18. Bohr Diagrams: Practice
Try drawing Bohr diagram for each of the following elements on your own: H He O Al
Ne - 10 electrons K Ne

19. Bohr Diagrams: Practice
Try drawing Bohr diagram for each of the following elements on your own: H He O Al Ne
K - 19 electrons K

20. Lewis Dot Diagrams
The electrons in the outermost shell are called ?

21. Lewis Dot Diagrams
The electrons in the outermost shell are called valence electrons.

22. Lewis Dot Diagrams
The electrons in the outermost shell are called valence electrons.
Lewis Dot Diagrams are abbreviated Bohr Diagrams that show just these outermost electrons, e.g.:

23. Valence Electrons and Families
Note that both hydrogen (H) and potassium (K) have just ? electron in their outermost shell.
Note also that these elements are both found in the ? column of the periodic table.
This is not a coincidence!

24. Valence Electrons and Families
Note that both hydrogen (H) and potassium (K) have just 1 electron in their outermost shell.
Note also that these elements are both found in the ? column of the periodic table.
This is not a coincidence!

25. Valence Electrons and Groups
Note that both hydrogen (H) and potassium (K) have just 1 electron in their outermost shell.
Note also that these elements are both found in the 1st column of the periodic table.
This is not a coincidence!

26. Valence Electrons and Groups
All elements in the same group (column) have the same number of electrons in their outermost shell (ref. p. 150).
It is these electrons that determine the behavior of the element, including how it reacts with other elements – and how it forms ions.

27. Valence Electrons and Groups
Let’s look at these groups or families in more detail

28. ALKALI METALS 1 valence electron (Hydrogen is not officially a member)
Soft and silvery metals
Very reactive, esp. with water

29. ALKALINE EARTH METALS 2 valence electrons White and malleable
Reactive, but less so

30. TRANSITION METALS
(the Groups in the middle)

31. BORON FAMILY
3 valence electrons
Most are metals
Boron is a metalloid.

32. CARBON FAMILY 4 valence electrons
Contains metals, metalloids, and a non-metal: carbon (C)

33. NITROGEN FAMILY 5 valence electrons
Contains metals, metalloids, and non-metals

34. OXYGEN FAMILY
6 valence electrons
Mostly non- metals
Reactive

35. Halogens
7 valence electrons
All are non- metals
Very reactive

36. Noble Gases Full outer shell Exist as gases
Not reactive with other elements
Do not form ions.

37. The Why of Ions
The Noble Gases do not react and do not form ions because they already have what all atoms want: full outer shells.

38. The How of Ions
Atoms will either gain electrons to fill their outer shell (as in the case of the non-metal chlorine)

39. The How of Ions
or lose electrons to go down to their last full shell (as in the case of the metal sodium)

40. Tune in next time
More details on the formation of ions will be revealed tomorrow.
For now, answer the questions:
p. 148 #1-5
p. 150 #1-3
p. 153 #10, 11