1. Objectives
To describe the formation of ions from their parent atoms
To learn to name ions
To predict which ion a given element forms by using the periodic table
To describe how ions combine to form neutral compounds

2. + What is the total of all the ‘+’ and ‘-’ ? - 4+ 4- -+
The total charge is zero. This is a neutral atom. All atoms start out neutral. - -

3. + What is the total if the atom loses an electron? - 4+ 3- - 1+
The total charge is 1+. This is a positive ion. Losing electrons makes the atom more positive. - -

4. + What is the total if the atom gains an electron? - - 4+ 5- - 1-
The total charge is 1-. This is a negative ion. Gaining electrons makes the atom more negative. - -

5. A. Ions
Atoms can form ions by gaining or losing electrons.
Metals tend to lose one or more electrons to form positive ions called cations.
Cations are generally named by using the name of the parent atom.

6. A. Ions
Nonmetals tend to gain one or more electrons to form negative ions called anions.
Anions are named by using the root of the atom name followed by the suffix –ide.

7. A. Ions
Ion Charges and the Periodic Table
The ion that a particular atom will form can be predicted from the periodic table. The most predictable are:
Elements in Group 1 (alkali metals) form 1+ ions
Elements in Group 2 (alkaline earth metals) form 2+ ions
Aluminum family metals form 3+ ions
Group 7 (halogens) form 1- ions
Group 6 (oxygen family) form 2- ions

8. A. Ions
Ion Charges and the Periodic Table

9. B. Compounds That Contain Ions
Ions combine to form ionic compounds.
Properties of ionic compounds
High melting points
Conduct electricity if ions can move:
If melted
If dissolved in water

10. B. Compounds That Contain Ions
Ionic compounds are electrically neutral.
The charges on the anions and cations in the compound must sum to zero.
Would these charge combinations work?
+2 -1
= +1 NO – not neutral
= 0 YES
= -1 NO – not neutral
= 0 YES

11. B. Compounds That Contain Ions
Formulas for Ionic compounds
Write the cation element symbol followed by the anion element symbol. (positive attitude goes first!)
The number of cations and anions must be correct for their charges to sum to zero.

12. Predict the ion formed by each element.
Sodium
Magnesium
Fluorine
Bromine
Oxygen
Calcium
Aluminum
Lithium
Chlorine
Na+
Mg2+ F-
Br -
O2-
Ca2+
Al3+
Li+
Cl-

13. Make the correct formulas from the ions below.
K+ and Cl-
Ba2+ and I-
Ga3+ and Br-
Sr2+ and O2-
Li+ and S2-
Al3+ and N3-
Cr3+ and O2-
KCl (1+ 1-)
BaI2 ( )
GaBr3 ( )
SrO
Li2S
AlN
Cr2O3

14. Make the correct formula for each pair of elements.
Magnesium and chlorine
Bromine and aluminum
Calcium and nitrogen
Mg Cl- Cl-  MgCl2
Positive
goes first
Br - Br - Br - Al3+  AlBr3
Ca2+ Ca2+ Ca2+ N3- N3-  Ca3N2