Download Chemical reactions occur with outer level electrons so that is the

Reassessment Practice
Chemistry Standard 3D: Charges/Oxidation numbers Name _____________________________________
Chemical reactions occur with outer level electrons so that is the focus of Chemistry
The most stable atoms have a full outer level or shell
The Octet Rule:
Atoms will combine to form compounds to reach 8 electrons in their outer energy level.
Atoms with less than 4 electrons will lose electrons
For Na it is easier to lose 1 electron than to gain 7 electrons
A Na atom has 11+ and 11- IF it loses one electron then 11+ and 10Atoms with more than 4 electrons will gain electrons
For Oxygen it is easier to gain 2 electrons than to lose 6 electrons
An O atom has 8+ and 8- IF it gains two electrons then 8+ and 10-
Oxidation numbers
This indicates the number of electrons an atom gained or lost when forming the compound.
Metals have positive oxidation numbers and nonmetal have negative oxidation numbers.
A
l
Aluminum has an oxidation number of +3.
+
A electrons. It needs to rid itself of 3 electrons to be stable. If it loses 3 electrons it will
Aluminum has 3 valence
have 10 electrons and 13 protons…… That’s +13 – 10 = +3 Charge
l
3 Aluminum is in the 13th column which is the +3 column
O
-
Oxygen has an oxidation number of -2.
Oxygen has 6 valence electrons. It needs 2 electrons to be stable. If it gains 2 electrons it will have 10
electrons and only2
8 protons…… That’s +8 – 10 = -2 Charge
Oxygen is in the 16th column which is the -2 column.
In the D block the Oxidation Numbers must be given for 99% of these metals elements.
Fe (III) is Iron Three and +3…..V (IV) is +4….Cu (II) is….+2. We will learn more about this later
Practice: List the oxidation numbers for these elements:
1. Li ____________
2. Mg __________
3. B _________
4. C _________
5. Na __________
6. Ca _________
7. Ga _______
8. Ge ________
9. Cs _________
10. Ba _________
11. In _______
12. P _________
13. S _________
14. Cl __________
15. Br _______
16. I __________
Why are there no noble gases listed here? ____________________________________________________
A cation is a _______________________________; an anion is a _________________________________