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.