1. Week 2: Cell chemistry: atoms and their ions
2.1 Arranging electrons in atoms [4.6]
2.2 Valence electrons [4.7]
2.3 Electron dot structures [4.7]
2.4 The formation of ions [6.1]
2.5 Cations and anions [6.1]
Readings: Chemistry Textbook. Timberlake (2015). Chemistry (12th edn.). Pearson Australia.
LFS103 Vol. 2 Custom textbook
Ch 4: Concepts 4.6, 4.7
Ch 6: Concept 6.1

2. Week 2: Learning objectives
Describe for the first 20 elements of the periodic table; the Z value, the valance electrons, the electron configuration and the electron dot structures.
Explain if an element is stable or reactive using its electron configuration.
Understand how an ion is formed.
Use the octet rule to write the symbols of the simple ions for the first 20 elements.
Explain which elements form cations and which elements form anions, and why.

3. Electron Dot Structures
This is a shorthand system for designating the number of valence electrons. They consist of an element’s symbol with one dot for each valence electron placed around the elemental symbol.

4. 2.3 Electron dot structures [4.7]

5. Electron Dot Structures
Period 2 Elements
Note: we have 4 single electrons around the atom before we start to pair electrons

6. 2.3 Electron dot structures [4.7]
Table 4.11, Timberlake (2015)

7. 2.3 Electron dot structures [4.7]
Atomic Size
2.3 Electron dot structures [4.7]
For the representative elements, the atomic radius:
increases down the Periodic Table in each Group due to the increasing number of electron shells.
decreases from left to right across each Period (row) in the Periodic Table due to the increasing number of protons pulling the electrons closer to the nucleus.
Atomic
radius

8. 2.3 Electron dot structures [4.7]
Figure 4.13, Timberlake (2015)

9. 2.3 Electron dot structures [4.7]
Oxygen (Z = 8 )
6 valence electrons
What is the electron dot diagram?
Shell 2 O
2e-
6e-
What is the electron configuration?
O 2, 6

10. Draw the electron dot diagram for Chlorine

11. Q. Which of the following is the correct electron dot structure for Phosphorus?
A) B) C) D)
ANSWER: C (one electron must fill each 1 or 4 pairs, before pairing can begin; i.e. 1 electron N, S, E W and then again, just as in answer C)