Post on 13-Jun-2015
Ionic Bonding - Binaryby
S. Sherman
Composition
• 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)
• Solid state• Tend to be crystalline• High melting points• Electrically neutral• Ionic bonds are very strong• High electronegativity differences• Formation of ionic bond is always
exothermic
Review
• Cations are positive ions formed from the loss of electrons
• Anions are negative ions formed from the gain of electrons
Oxidation States
• 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!
Review
• Nonmetal ions are named with the nonmetal name followed by an –ide
• Sulfur sulfide, phosphorous phosphide, nitrogen nitride etc.
Review – Name these ions
• Na+
• Ca2+
• Al3+
• Fe3+
• Fe2+
• Pb2+
• Zn2+
Answers:
• Sodium ion
• Calcium ion
• Aluminum ion
• Iron (III)ion
• Iron (II)ion
• Lead (II) ion
• Zinc ion
Review – Name these:
• P3-
• S2-
• N3-
• O2-
• F-
• Cl-
• I-
Answers (make sure you spelled correctly!):
• Phosphide ion
• Sulfide ion
• Nitride ion
• Oxide ion
• Fluoride ion
• Chloride ion
• Iodide ion
Writing Ionic Formulas
Objectives:
• 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
monatomicTernary 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!
Na Cl
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 Ba2+ (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!
Picture Explanation
Ba Cl
Cl
Final formula: BaCl2 (1:2) ratio
Aluminum Sulfide
Comes from the aluminum atom combining with the sulfur atom (forming ions in process):
Aluminum ion Al3+ (loses 3 electrons)
Sulfide ion S2- (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!
Picture Explanation
Al S
Al S
S
Final formula Al2S3 (2:3 ratio)
Practice! Write formula for:
1. Magnesium + Oxygen
2. Sodium + Nitrogen
3. Barium + Phosphorus
4. 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
Mg2+ O2- MgO
Sodium and Nitrogen
Na+ N3- Na3N
Barium and Phosphorus
Ba2+ P3- Ba3P2
Aluminum and Bromine
Al3+ Br- AlBr3
Tin (IV) and Sulfur
Sn4+ S2- SnS2
Writing Names
• 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
Examples
• MgO magnesium oxide (only 1 possible charge so no roman numeral)
• MnO manganese (II) oxide (multiple charges need roman numeral)
Oxide ion is O2-, 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
Examples
• MnO2 manganese (IV) oxide
Oxide ion is O2- (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!
Picture example
MnO comes from Mn O
+2 cation = manganese (II)
MnO2 comes from Mn O
O
+ 4 cation = manganese (IV)
Naming Practice:
1-5. Go back and name the formulas on the previous practice!
Also Name:
6. ReS3
7. CaS8. PbO
9. Ag2O
10. FeF3
Answers – Check your spelling!Elements Cation Anion Formula Name
Magnesium and Oxygen
Mg2+ O2- MgO Magnesium Oxide
Sodium and Nitrogen
Na+ N3- Na3N Sodium Nitride
Barium and Phosphorus
Ba2+ P3- Ba3P2 Barium Phosphide
Aluminum and Bromine
Al3+ Br- AlBr3 Aluminum Bromide
Tin (IV) and Sulfur
Sn4+ S2- SnS2 Tin (IV) Sulfide
Answers (spelling counts!):Formula Cation Anion Name
ReS3 Re6+ S2- Rhenium (VI) Sulfide
CaS Ca2+ S2- Calcium Sulfide
PbO Pb2+ O2- Lead(II) Oxide
Ag2O Ag+ O2- Silver Oxide
FeF3 Fe3+ F- Iron (III) Fluoride
Independent Practice
Complete the binary ionic bonding practice handout – by yourself!
You should only use the periodic table you were provided.