ionic vs. covalent, nomenclature, and chemical reactions naming and identifying chemical compounds...
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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