Writing and Naming Chemical Compounds

Ionic Compounds

Review:

+1 +2   +3 ±4 -3 -2 -1 0

Common Oxidation Numbers (Charges)

Cation- Positive ion that has LOST electrons (Metals)Anion- Negative Ion that has GAINED electrons (Nonmetals)

Polyatomic Ions you MUST know:

Nitrate NO3-

Carbonate CO3-2

Sulfate SO4-2

Phosphate PO4-3

Hydroxide OH-

Acetate C2H3O2- (CH3COO-)

Ammonium NH4+

Remember polyatomic ions STAY TOGETHER!!!!

Bonding Review:

Ionic compounds are formed when a metal transfers electrons to a nonmetal Cation (metal) + Anion (nonmetal) = Ionic bond Cation (metal) + Polyatomic Ion = Ionic bond Polyatomic ion + Anion (nonmetal) = Ionic bond Polyatomic Ion + Polyatomic Ion = Ionic bond

Writing Formulas for Ionic Compounds

Rules: The symbol tells the element and the subscript

(little number to the right of the symbol) tells how many of each element is in the formula

The cation (metal ion) or positively charged polyatomic ion is always written first and the anion (nonmetal ion) or negatively charged polyatomic ion is always written second

Writing Formulas for Ionic Compounds

1) Start by writing the cation and anion separately with their charges

Ex: If you want to write the chemical formula for magnesium and chlorine

Mg+2 and Cl-1

2) Criss-cross the charges so that they become the subscripts but drop the +/- signs

Ex: The +2 charge from Mg will become the 2 subscript for Cl and the -1 charge from Cl will become the 1 subscript for Mg

Mg1Cl2 (You don’t have to write the 1 so the formula correctly written would be MgCl2)

3) Reduce the subscripts if they can be reduced. In this case, they can’t, so you are done!!!

Now You Try!

1) lithium and fluorine 2) calcium and sulfur 3) cesium and oxygen 4) aluminum and oxygen 5) sodium and sulfur 6) aluminum and chlorine 7) potassium and oxygen

Check Your Answers:

1) LiF 2) CaS 3) Cs2O

4) Al2O3

5) Na2S

6) AlCl3 7) K2O

Writing Ionic Formulas for Compounds with Polyatomic Ions

1) Start by writing your anion and cation with their charges separately

If your anion or cation is a polyatomic ion, place parenthesis around it and put the charge on the outside of the parenthesis

Ex: If you are writing the formula for sodium and carbonate: Na+1 and (CO3)-2

2) Criss-cross the charges so that they become the subscripts but drop the +/- signs

Place the subscript on the outside of the parenthesis of your polyatomic ion. MAKE SURE NOT TO SEPARATE WHAT WAS INSIDE THE PARENTHESIS!!!

Ex: Na2(CO3)

Now You Try!

1) aluminum and nitrate 2) magnesium and phosphate 3) ammonium and chlorine 4) calcium and acetate 5) sodium and hydroxide

Check Your Answers:

Al(NO3)3

Mg3(PO4)2

(NH4)Cl

Ca(C2H3O2)2

Na(OH)

Oxidation Number Exceptions

Since the oxidation numbers of transition metals cannot be predicted by looking at the group numbers, you will need to memorize the oxidation numbers for these exceptions Ag+1

Zn+2

Cd+2

Hg2+2 mercury (I)

Hg+2 mercury (II)

These Roman Numerals will make since in about 3 slides

Naming Binary Ionic Compounds

Binary means there are only two elements in the compound

Rules for Naming: 1) Name the metal 2) Shorten the name of the non-metal and add

the suffix “– ide”

Ex: KCl would be named potassium chloride

Now You Try!

Name the following compounds: 1) MgBr2

2) NaF 3) Al2O3

4) CdO 5) ZnS 6) Na2O

7) K3N

Check Your Answers:

1) magnesium bromide 2) sodium fluoride 3) aluminum oxide 4) cadmium oxide 5) zinc sulfide 6) sodium oxide 7) potassium nitride

Naming Ionic Compounds with Transition metals Since the oxidation numbers of transition metals cannot be

predicted by looking at the group numbers, a roman numeral must be used to name the oxidation state of the transition metal in a compound Transition metals can have more than one oxidation number

(charge) The only exception to this rule is when naming the transition

metals you were told to memorize (silver, zinc, cadmium, mercury still needs a roman numeral)

To find the roman numeral, you must WORK BACKWARDS and uncriss-cross your charges! Ex: FeCl2 uncriss-crossed is Fe+2 and Cl-, so the Roman numeral

when naming iron is (II) therefore the name of the compound is iron (II) chloride

Now You Try!

1) SnO 2) CuS 3) Hg2I2

4) CuI 5) PbO2

Check Your Answers:

1) tin (II) oxide 2) copper (II) sulfide 3) mercury (I) iodide 4) copper (I) iodide 5) lead (IV) oxide

So how do you write the formula for a compound with a transition metal?

Same process as naming ionic compounds only the Roman numeral is the oxidation number, so use it as the charge! Iron (III) oxide

EX: Fe+3 and O-2 is written Fe2O3

Now You Try!

Write the formula for the following compounds: 1) Tin (IV) chloride 2) Lead (IV) oxide 3) Tin (II) sulfide 4) Mercury (II) bromide 5) Mercury (I) fluoride 6) Copper (II) nitride 7) Iron (II) iodide

Check Your Answers:

1) SnCl4 2) PbO2

3) SnS 4) HgBr2

5) Hg2F

6) Cu3N2

7) FeI2

Naming Ionic Compounds with Polyatomic Ions

Rules for naming:1) Name the metal or positively charge polyatomic ion first

2) If the anion is a polyatomic ion, just name the polyatomic ion as is. If the anion is a non-metal replace the ending with –ide just like you would if you had a regular binary compound If you have two polyatomic ions, name the positively

charged poly first followed by the negatively charged poly Ex: Al(NO3)3 would be named aluminum nitrate

Ex: (NH4)Cl would be named ammonium chloride

Ex: (NH4)(NO3) would be named ammonium nitrate

Molecular Compounds

Review:

Molecular compounds are formed when two nonmetals form a covalent bond

These compounds are called molecules Covalent bonds are the result of atoms sharing

electrons Nonmetal + nonmetal = molecule

Naming Molecular Compunds

We use Greek Prefixes to indicate the number of atoms of each element that are present 1- mono (not used if for the first element) 2- di 3- tri 4- tetra 5- penta 6- hexa 7- hepta 8- octa 9- nona 10- deca

Naming Molecular Compounds

Rules for naming: 1) Name the first element using the appropriate

prefix that indicates how many atoms are present If there is only 1 element present you do not name it

using mono 2) Name the second element using the

appropriate prefix and change the ending to –ide EX: CO would be named carbon monoxide EX: Cl2O7 would be named dichlorine heptoxide

Now You Try!

1) CO2

2) N2O3

3) Cl2O

4) SO3

5) P4O10

Check Your Answers:

1) carbon dioxide 2) dinitrogen trioxide 3) dichlorine monoxide 4) sulfur trioxide 5) tetraphosphorus decoxide

Naming Acids

Compounds which have hydrogen written as the cation and have the physical state (aq) written next to them are acids If any other physical state is noted, (g) (s) or (l), the

compound is named like a regular binary compound These compounds are named hydro (nonmetal)ic

acid EX: HCl (aq) is named hydrochloric acid

If a hydrogen is written in front of a polyatomic ion the compound is named (poly)ic acid EX: H(NO3) (aq) is named nitric acid

Now You Try!

1) HF (aq) 2) H2S (aq)

3) H3P (aq)

4) H2(SO4) (aq)

5) H3(PO4) (aq) 6) HBr (l)

Check Your Answers:

1) Hydrofluoric acid 2) Hydrosulfuric acid 3) Hydrophosphoric acid 4) Sulfuric acid 5) Phosphoric acid 6) Hydrogen bromide

Diatomic Elements

There are 7 elements that can’t exist as single atoms in nature so they must be written as two atoms when they are not combined into compounds

They are just called by their elemental names You must MEMORIZE these:

Hydrogen, H2

Oxygen, O2

Nitrogen, N2

Fluorine, F2

Chlorine, Cl2 Bromine, Br2

Iodine, I2

You can remember these: H. BrONClIF