1. Ions, Valences and Oxidation Numbers

2. Formation of ions from atomsX X +
sodium ion
11Na+ 2, 8
one electron transferred X
17Cl- 2, 8, 8 X -
chloride ion
sodium atom X
chlorine atom
11Na 2, 8, 1
17Cl 2, 8, 7

3. Rule of Octet
An atom is most stable when it’s outer e- shell is filled (except for H which is 2, that number is 8)
Valence e- are the # of e- in the outer shell. In the main groups, the valence # is the last digit of the group.
Oxidation # can refer to a couple of things:
a. The charge of a monoatomic ion
b. In a molecule or polyatomic ion the
oxidation # is the value of a “pseudo-charge”

4. A polyatomic ion (list on pg 268):
A monoatomic ion:
Na has only 1 valence e-, when it becomes an ion its oxidation number is +1 because it loses that ion.
Oxidation value of these tend to be constant and are formed according to the rule of octet.
A polyatomic ion (list on pg 268):
Is an ion like NO3- or PO4-3; they don’t
split up very easily/are involved in chemical reactions as a unit.
Compounds have oxidation values of 0 because the individual ion charges have cancelled out.

5. Formation of positive ion from its atomX +
sodium ion
11Na+ 2, 8
sodium atom X
11Na 2, 8, 1

6. Formation of positive ion from its atomX + X
sodium atom
loses one electron
to form sodium ion with 1+ charge
11Na+ 2, 8
by losing an electron from its outer energy shell
11Na 2, 8, 1

7. Formation of negative ion from its atomX
17Cl- 2, 8, 8 X -
chloride ion
chlorine atom
17Cl 2, 8, 7

8. Formation of negative ion from its atomX X -
chlorine atom
gains one electron
to form chloride ion with 1- charge
by gaining an electron in its outer energy shell
17Cl 2, 8, 7
17Cl- 2, 8, 8

9. Lewis Dot Structures
Lewis Dot structures are used to symbolize the location of electrons in the outermost energy level.
These are useful in determining how an atom will bond.
Each electron is represented with a dot around the symbol of the element.
Each element can have a maximum of 8 electrons around it.

10. Practice examples