Ionic compounds consist of metal cations bonded with nonmetal anions
Transfer of electrons
Electrons lost by cation are gained by anion
The cation and anions surround each other
Smallest particle is a formula unit
Properties (of an ionic compound)
Tend to be crystalline
High melting points
Ionic bonds are very strong
High electronegativity differences
Formation of ionic bond is always exothermic
Cations are positive ions formed from the loss of electrons
Anions are negative ions formed from the gain of electrons
Cations with only one oxidation number are named with the name of the element followed by the word ion (groups 1, 2, 13,14)*
*Note: need to know that lead (Pb) and tin (Sn) have multiple charges (both can be 2+ or 4+)
Carbon in group 14 does not form ions - it forms covalent bonds (share) instead.
Cations with multiple oxidation states ( transition metals ) are named with the metal name followed by a roman numeral representing the oxidation state and the word ion *Note: Silver is always +1, Cadmium and Zinc are always +2 : learn these transition metal exceptions!
Nonmetal ions are named with the nonmetal name followed by an –ide
Sulfur sulfide, phosphorous phosphide, nitrogen nitride etc.
Review – Name these ions
Lead (II) ion
Review – Name these:
Answers (make sure you spelled correctly!):
Writing Ionic Formulas
balance the electrons lost and gained
Write formula with lowest possible ratio with this balance of electron transfer
Final formula is neutral
Two types of Ionic Bonding
Binary ionic bonding:
Composed of two elements
One cation and one anion – both monatomic
Ternary ionic bonding:
Composed of three or more elements
One cation and one anion – must contain at least one polyatomic ion (will discuss later)
Writing Formulas - Binary
Sodium chloride comes from the sodium atom and chlorine atom combined (forming ions in process):
Sodium ion Na + (losing one electron)
Chloride ion Cl - (gaining one electron)
The electron lost by the sodium atom to transferred to the chloride ion
Picture Explanation (use your dot diagrams)
Copy from board!
Final chemical formula: NaCl (1:1 ratio)
Barium Chloride – writing formula
Composed of barium atom combined with chlorine atom (forming ions in process)
Barium ion Ba 2+ (loses two electrons)
Chloride ion Cl - (gains one electron)
You need two of the chlorine atoms to each gain one electron to combine with one atom of barium losing two electrons to balance the transfer of electrons!
Final formula: BaCl 2 (1:2) ratio
Comes from the aluminum atom combining with the sulfur atom (forming ions in process):
Aluminum ion Al 3+ (loses 3 electrons)
Sulfide ion S 2- (gains 2 electrons)
Must balance the charges – find lowest common denominator need to lose 6 and gain 6 total
Need 2 Al atoms each losing 3 electrons to balance with 3 sulfur atoms each gaining 2 electrons!
Final formula Al 2 S 3 (2:3 ratio)
Practice! Write formula for:
Magnesium + Oxygen
Sodium + Nitrogen
Barium + Phosphorus
Aluminum + Bromine
5. Tin (IV) + Sulfur
Make columns for: cation, anion, formula and name (will add later) in your notebook
Elements Cation Anion Formula Magnesium and Oxygen Mg 2+ O 2- MgO Sodium and Nitrogen Na + N 3- Na 3 N Barium and Phosphorus Ba 2+ P 3- Ba 3 P 2 Aluminum and Bromine Al 3+ Br - AlBr 3 Tin (IV) and Sulfur Sn 4+ S 2- SnS 2
For formulas with cations that only have one charge, just write the name of the two ions without the word ion
For formulas with cations that have multiple charges (transition metals) you need to look at the charge on the anion to determine the charge of the cation
MgO magnesium oxide (only 1 possible charge so no roman numeral)
MnO manganese (II) oxide (multiple charges need roman numeral)
Oxide ion is O 2- , and there is a 1:1 ratio of ions in the formula MnO therefore the charge on Mn must be +2 to balance the charge and get that formula
MnO 2 manganese (IV) oxide
Oxide ion is O 2- (gains 2 electrons) and you have two atoms of oxygen in the formula so the total electrons gained is x 2 = 4
Therefore, the one atom of manganese needs to lose 4 electrons!
MnO comes from Mn O
+2 cation = manganese (II)
MnO 2 comes from Mn O
+ 4 cation = manganese (IV)
1-5. Go back and name the formulas on the previous practice!
6. ReS 3
9. Ag 2 O
10. FeF 3
Answers – Check your spelling! Elements Cation Anion Formula Name Magnesium and Oxygen Mg 2+ O 2- MgO Magnesium Oxide Sodium and Nitrogen Na + N 3- Na 3 N Sodium Nitride Barium and Phosphorus Ba 2+ P 3- Ba 3 P 2 Barium Phosphide Aluminum and Bromine Al 3+ Br - AlBr 3 Aluminum Bromide Tin (IV) and Sulfur Sn 4+ S 2- SnS 2 Tin (IV) Sulfide
Answers (spelling counts!): Formula Cation Anion Name ReS 3 Re 6+ S 2- Rhenium (VI) Sulfide CaS Ca 2+ S 2- Calcium Sulfide PbO Pb 2+ O 2- Lead(II) Oxide Ag 2 O Ag + O 2- Silver Oxide FeF 3 Fe 3+ F - Iron (III) Fluoride
Complete the binary ionic bonding practice handout – by yourself!
You should only use the periodic table you were provided.