Ionic vs. Covalent, Nomenclature, and Chemical Reactions Naming and identifying chemical compounds...

Ionic vs. Covalent, Nomenclature, and Chemical

Reactions

Naming and identifying chemical compounds and reactions

Covalent Bonding

Covalent Bond: A bond that results when two atoms share several (usually two) electrons.

Covalency is greatest between atoms when electronegativities are similar.

Ionic Bonding

Ionic Bond: A bond that results when two atoms have exchanged electrons.

Ionicity is greatest between atoms when electronegativities are significantly different.

Ionic BondsIn the formation of sodium chloride, one electron is transferred from the sodium atom to a chlorine atom.

11 protons11 electrons

17 protons17 electrons

Na+ + Cl–Na + Cl2

11 protons10 electrons

17 protons18 electrons

Cation: A positively charged particle. Metals tend to lose electron(s) and form cations.

Anion: A negatively charged particle. Nonmetals tend to gain electron(s) and form anions.

Metals vs. Nonmetals

•Metals tend to have low IONIZATION ENERGY

They tend to lose one or more electrons.

•Nonmetals tend to have high ELECTRON AFFINITY

They tend to gain one or more electrons.

Electronegativity

For ionic compounds, you need large electronegativity differences between atoms. General rule is ionic bonds are formed between a metal (becomes cation when loses electron(s)) and a nonmetal (becomes anion when gains electron(s)). Electrons are “transferred”.

For covalent compounds, you need minimal electronegativity differences between atoms. General rule is covalent bonds are formed between two nonmetals. Electrons are “shared”.

Ionic or Covalent?

BaCl2 Cr(NO3)6

FePO4 CuSO3

Si2S4 N2O3

Al3N2 K3P

Flow Chart to follow

Prefixes

1 mono 7 hepta

2 di 8 octa

3 tri 9 nona

4 tetra 10 deca

5 penta

6 hexa 12 dodeca

Compounds containing semimetals are named like compounds containing all nonmetals (covalent compounds).

Worked Example Naming Binary Molecular Compounds

Look at a periodic table to see which element in each compound is more cationlike (less electronegative; farther to the left or lower) and which is more anionlike (more electronegative; farther to the right or higher). Then name the compound using the appropriate numerical prefix.

Solution

a. Phosphorus trichloride b. Dinitrogen trioxidec. Tetraphosphorus heptoxide d. Bromine trifluoride

Strategy

Give systematic names for the following compounds:a. PCl3 b. N2O3 c. P4O7 d. BrF3

Criss Cross: Going from Formula to Name

Criss crossing is only used for ionic compounds that contain weird charges like transition metals. Group 1A and 2A metals, the charge is known and is +1 and +2, respectively. ALWAYS IDENTIFY THE COMPOUND AS IONIC OR COVALENT FIRST.

Criss Cross: With Transition Metal

FeCl2

FeCl2Fe2 Cl1

Fe+2 Cl-1

More electronegative species will carry negative charge meaning it will gain the electrons. Chlorine is in Group 7A and wants to get to 8. How many electrons will it gain? 1e

Since Fe comes first and is the metal, it will have a positive charge (cation). Likewise, Cl comes second and will have a negative charge (anion). Criss Cross and add positive and negative sign.

Iron is +2 so we give roman numeral of II. This is iron (II) chloride.

iron (II) chloride

Criss Cross: With Transition Metal

FeCl3

FeCl3Fe3 Cl1

Fe+3 Cl-1

More electronegative species will carry negative charge meaning it will gain the electrons. Chlorine is in Group 7A and wants to get to 8. How many electrons will it gain? 1e

Since Fe comes first and is the metal, it will have a positive charge (cation). Likewise, Cl comes second and will have a negative charge (anion). Criss Cross and add positive and negative sign.

Iron is +3 so we give roman numeral of III. This is iron (III) chloride.

iron (III) chloride

Criss Cross: Difficult

PbS

PbS

Pb1 S1

Pb+1x2 S-1x2

Pb+2 S-2

More electronegative species will carry negative charge meaning it will gain the electrons. Sulfur is in Group 6A and wants to get to 8. How many electrons will it gain? 2e

Criss cross does not work. We already know sulfur is -2. But criss crossing gets us -1. To get from -1 to -2, we have to multiply by common factor of 2.

We now know Pb is +2 so we give roman numeral of II. This is lead (II) sulfide.

lead (II) sulfide

Criss Cross: Difficult

PbS2

PbS2

Pb2 S1

Pb+2x2 S-1x2

Pb+4 S-2

More electronegative species will carry negative charge meaning it will gain the electrons. Sulfur is in Group 6A and wants to get to 8. How many electrons will it gain? 2e

Criss cross does not work. We already know sulfur is -2. But criss crossing gets us -1. To get from -1 to -2, we have to multiply by common factor of 2.

We now know Pb is +4 so we give roman numeral of IV. This is lead (IV) sulfide.

lead (IV) sulfide

Naming Binary Compounds

CaCl2 CrBr3

C2S4 NO2

Fe3N2 Na3P

Determining Formulas from Names

How do charges help you decide subscripts?

Look up the charges for each element (or polyatomic ion). Determine the least common multiple between the two charges. The factor each charge needs to be multiplied by to give the least common multiple will be the subscript for that element.

Criss Cross: Going from Name to Formula

Criss Cross

lead (II) sulfide

Pb+2 S-2

Pb+2 S-2

Pb2S2

More electronegative species will carry negative charge meaning it will gain the electrons. Sulfur is in Group 6A and wants to get to 8. How many electrons will it gain? 2e

What is the least common multiple? 22This can be simplifiedThis can be simplified

PbS

Drop the positive or negative sign when you criss cross.

Criss Cross

lead (IV) sulfide

Pb+4 S-2

Pb+4 S-2

Pb2S4

More electronegative species will carry negative charge meaning it will gain the electrons. Sulfur is in Group 6A and wants to get to 8. How many electrons will it gain? 2e

What is the least common multiple? 22This can be simplifiedThis can be simplified

PbS2

Criss Cross

iron (II) chloride

Fe+2 Cl-1

Fe+2 Cl-1

Fe1Cl2

More electronegative species will carry negative charge meaning it will gain the electrons. Chlorine is in Group 7A and wants to get to 8. How many electrons will it gain? 1e

What is the least common multiple? NoneNone This is already simplifiedThis is already simplified

FeCl2

Criss Cross

iron (III) chloride

Fe+3 Cl-1

Fe+3 Cl-1

Fe1Cl3

More electronegative species will carry negative charge meaning it will gain the electrons. Chlorine is in Group 7A and wants to get to 8. How many electrons will it gain? 1e

What is the least common multiple? NoneNone This is already simplifiedThis is already simplified

FeCl3

Finding Formulas

copper(II) chloride aluminum nitride

calcium bromide iron(III) sulfide

carbon disulfide dibromine monoxide

barium fluoride disilicon tetrachloride

Polyatomic Ions

Ions composed of more than one atom.

You will need to learn their names, formulas and charges.

Polyatomic IonsPolyatomic means composed of more than 1 atom. A big exception to the metal with a nonmetal rule for ionic compounds comes from NH4

+ in for example NH4Cl. Here everything is nonmetal but still ionic b/c of charges (ions)

Polyatomic Ions

Naming Ionic Compounds

Polyatomic Ionic Compounds

sodium carbonate: Na2CO3Na+ CO32–

iron(II) hydroxide: Fe(OH)2Fe2+ OH–

magnesium carbonate: MgCO3Mg2+ CO32–

sodium hydroxide: NaOHNa+ OH–

Naming Compounds with Polyatomics

Ca(NO3)2 CrPO4

Na2CO3 (NH4)3PO4

Fe3(SO4)2 Li3ClO3

Easiest way to identify a polyatomic containing compound is to look at the compound and see if it consists of more than 2 elements. If it does, it is polyatomic. Also, most of the polyatomic ions contain oxygen. KEEP POLYATOMIC IONS GROUPED FOR CRISS CROSSING.

Finding Formulas with Polyatomics

copper(II) chlorate aluminum nitrate

calcium phosphate iron(III) sulfate

sodium acetate barium hydroxide

strontium carbonate

Day 1

Nitrate NO3-1

Chlorate ClO3-1

Bromate BrO3-1

Iodate IO3-1

Carbonate CO3-2

Sulfate SO4-2

Phosphate PO4-3

Day 2

Nitrite NO2-1

Chlorite ClO2-1

Sulfite SO3-2

Hydrogen Phosphate HPO4-2

Dihydrogen Phosphate H2PO4-1

Hydrogen Carbonate HCO3-1

(bicarbonate)

Hydrogen Sulfate HSO4-1

Day 3

Permanganate MnO4-1

Hypochlorite ClO-1

Perchlorate ClO4-1

Periodate IO4-1

Acetate C2H3O2-1

Chromate CrO4-2

Dichromate Cr2O7-2

Day 4

Peroxide O2-2

Cyanide CN-1

Hydroxide OH-1

Arsenate AsO4-3

Oxalate C2O4-2

Ammonium NH4+1

Chemical Reactions

Symbols seen in a reaction.

(g) gaseous

(s) Solid

(l) liquid

(aq) aqueous (dissolved in water)

heat applied

Parts of a reaction

Reactants: beginning chemicals in a reaction.

Products: chemicals formed from a reaction.

Coefficients: numbers in front of chemical symbols indicating the number of moles of each chemical involved in the reaction.

Writing a reaction.

Make sure all the subscripts are correct (check charges, or use prefixes when going from words to formulas)

Make sure you have the same number of each element on both sides of the reaction.

Coefficients and subscripts multiply to determine the amount of each element. Use coefficients to balance reactions.

Example 1

Write the formulas for each reaction and balance:

1.Aluminum chloride + sodium carbonate aluminum carbonate + sodium chloride

2.Iron(II)oxide + potassium iodide iron(II)iodide + potassium oxide

3.Calcium phosphate + chromium(III)nitride calcium nitride + chromium phosphate

Types of Reactions

* Synthesis, Composition, Combination

*Single Replacement, Single Displacement

*Double Replacement, Double Displacement

*Decomposition

*Combustion

Diatomic elements

H,O,N,Cl,Br,I,F

*Everything else can be written monatomically.

Ex: Iron can be written as Fe (this is elemental form)

Synthesis (S)

A + B AB

H2 + O2

Sodium + chlorine

Zinc + oxygen

Synthesis (S)

A + B AB

2H2 + O2 2H2O

Sodium + chlorine 2Na + Cl2 2NaCl

Zinc + oxygen 2Zn + O2 2ZnO

Single Replacement

A + BC AC + B

Zinc + hydrochloric acid

Sodium + Aluminum nitrate

Calcium + water

*Group 1A or 2A metals reacting with water, write water as HOH

Single Replacement

A + BC AC + B

Zinc + hydrochloric acid Zn + 2HCl ZnCl2 + H2

Sodium + Aluminum nitrate 3Na + Al(NO3)3 3NaNO3 + AlCalcium + water Ca + 2HOH Ca(OH)2 + H2

*Group 1A or 2A metals reacting with water, write water as HOH

Double Replacement

AB + CD AD + CB

Silver(I)nitrate + Calcium chloride

Barium hydroxide + hydrofluoric acid

Aluminum oxide + magnesium iodide

Double Replacement

AB + CD AD + CB

Silver(I)nitrate + Calcium chloride 2AgNO3 + CaCl2 2AgCl + Ca(NO3)2

Barium hydroxide + hydrofluoric acid Ba(OH)2 + 2HF BaF2 + 2HOH

Aluminum oxide + magnesium iodide Al2O3 + 3MgI2 2AlI3 + 3MgO

Decomposition:

AB A + B

Mercury(II)oxide

Aluminum chloride

Decomposition:

AB A + B

Mercury(II)oxide 2HgO 2Hg + O2

Aluminum chloride 2AlCl3 2Al + 3Cl2

Decomposition of polyatomic ions

Metal chlorate metal chloride + O2

Metal carbonate metal oxide + CO2

Metal hydroxide metal oxide + H2O

Metal Chlorates

Potassium chlorate

Calcium chlorate

Iron(III)chlorate

Metal Chlorates

Potassium chlorate 2KClO3 2KCl + 3O2

Calcium chlorate Ca(ClO3)2 CaCl2 + 3O2

Iron(III)chlorate Fe(ClO3)3 FeCl3 + 4.5O2 OR

2Fe(ClO3)3 2FeCl3 + 9O2

Metal Carbonates

Calcium carbonate

Aluminum carbonate

Copper(I)carbonate

Metal Carbonates

Calcium carbonate CaCO3 CaO + CO2

Aluminum carbonate Al2(CO3)3 Al2O3 + 3CO2

Copper(I)carbonate Cu2CO3 Cu2O + CO2

Metal Hydroxides

Sodium hydroxide

Chromium(III)hydroxide

Magnesium hydroxide

Metal Hydroxides

Sodium hydroxide 2NaOH Na2O + H2O

Chromium(III)hydroxide 2Cr(OH)3 Cr2O3 + 3H2O

Magnesium hydroxide Mg(OH)2 MgO + H2O

CombustionCxHy + O2

CO2 + H2O

CxHyOz + O2

To balance, start with hydrogen, then carbon, end with oxygen.

C8H18 + O2

C2H6O + O2

CombustionTo balance, start with hydrogen, then

carbon, end with oxygen.

C8H18 + 12.5O2 8CO2 + 9H2O OR

2C8H18 + 25O2 16CO2 + 18H2O

C2H6O + 3O2 2CO2 + 3H2O