Naming and Bonding Notes.notebook
February 16, 2016
Matter
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Pure Substances
Mixtures
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Elements
Compounds
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Homogeneous
Heterogeneous
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Solutions
Colloids
Suspensions
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Feb 15­1:26 PM
Chemical formulas tell 2 things
1. letters: elements in the compound
2. numbers: numbers of atoms of each element
example: Al2(SO4)3 has 3 elements (Al, S, O) and
17 atoms (2 Al, 3 S, 12 O)
Binary compound: a compound made up of only 2 elements (NaCl)
Ternary compound: a compound made up of 3 elements (NaNO3)
Polyatomic compound: a compound made up of more than 3 elements ((NH4)2Cr2O7)
Feb 15­1:31 PM
Naming and Bonding Notes.notebook
February 16, 2016
General Rules for Nomenclature
All binary compounds end in “‐ide”, but not all compounds
that end in “‐ide” are binary.
Examples: NaOH (sodium hydroxide), NaCN (sodium
cyanide)
All compounds are neutral, so the total number of positives
must equal the total number of negatives.
Example: AlBr3 = Al3+ and 3 Br1‐ = 3+ + 3(1‐) = 0
The element with the (+) charge (oxidation number) is written
first in a formula
Feb 15­1:33 PM
Rules for Binary Ionic Compounds
Ionic compounds are made up of a metal (cation) and nonmetal(s) (anion)
Ionic compounds are represented by formula units‐ the simplest combining ratio between
ions in a compound. A formula unit is an empirical formula.
Naming Binary Ionic Compounds
1. Write the name of the cation. If the cation is a transition element, use the Stock
System (a Roman numeral) to show the charge (oxidation number) of the transition
element.
DO NOT use one for Ag+ (it’s always 1+) or Zn2+ (it’s always 2+).
DO USE one for Pb2+ or Pb4+ or Sn2+ or Sn4+
2) Write the name of the anion. Change the ending to “‐ide.”
NaCl
CuO
CaBr2
Cu2O
ZnCl2
PbO2
Feb 15­1:35 PM
Naming and Bonding Notes.notebook
Writing
1.
2.
3.
4.
5.
February 16, 2016
Binary Ionic Formulas
Write the formula for the cation, include the charge!
Write the formula for the anion, include the charge!
Criss‐cross the numeric part of the charge (oxidation number) to use as subscripts
Simplify if needed
Check to make sure that the number of positives equals the number of negatives
aluminum sulfide
lead (II) oxide
silver bromide
titanium (VI) chloride
Feb 15­1:39 PM
Rules for Ternary Ionic Compounds
Ternary ionic compounds are made up of a metal (cation) and polyatomic anion.
Treat a polyatomic ion as a unit. Place it in parentheses unless its subscript is one. DO
NOT CHANGE any of its subscripts! You will destroy its identity!
Naming Ternary Ionic Compounds
1. Write the name of the cation. If the cation is a transition element, use the
Stock System (a Roman numeral).
2. Write the name of the polyatomic anion.
NaNO3
CuOH
Ca(C2H3O2)2
Na3PO4
PbSO4
Al2(SO4)3
Feb 15­1:41 PM
Naming and Bonding Notes.notebook
Writing
1.
2.
3.
4.
5.
February 16, 2016
Ternary Ionic Formulas
Write the formula for the cation, include the charge!
Write the formula for the polyatomic anion, include the charge!
Criss‐cross the numeric part of the charge (oxidation number) to use as subscripts
Simplify if needed; protect the polyatomic ion with parentheses!
Check to make sure that the number of positives equals the number of negatives
barium sulfate
copper (II) nitrate
tin (IV) phosphate
ammonium hydroxide
3(4+) + 4(3‐) = 0
Feb 15­1:42 PM
Rules for Binary Molecular Compounds
Molecular compounds are made up of nonmetals.
A molecular formula may or may not be an empirical formula. Example: H2O (water) is
an empirical formula; C6H6 (benzene) is not.
Use prefixes to indicate the number of atoms of each element in the formula.
Do not begin a name with “mono‐”
mono‐
1
penta‐
5
nona‐
9
di‐
2
hexa‐
6
deca‐
10
tri‐
3
hepta‐
7
undeca‐
11
tetra‐
4
octa‐
8
dodeca‐
12
Feb 15­1:44 PM
Naming and Bonding Notes.notebook
February 16, 2016
Naming Molecular Compounds
1. Write the name of the first element. If there is a subscript, use the appropriate
prefix.
2. Write the name of the second element. If there is a subscript, use the appropriate
prefix. Change the ending to “‐ide.”
CO
CO2
P2O5
N2 O
SO3
P4O10
Feb 15­1:50 PM
Writing Molecular Formulas
The prefix system tells you each subscript! If no prefix is given for the first element, it’s a
“mono‐.”
dinitrogen pentoxide
carbon tetrachloride
phosphorus pentachloride
xenon hexafluoride
Feb 15­1:56 PM
Naming and Bonding Notes.notebook
February 16, 2016
Rules for Naming Acids
Acids are aqueous solutions of hydrogen compounds
Binary Acids (HAXB)
Are always named as HYDRO+(root of anion)+IC ACID
Ternary Acids (HAXYB)
Are always named after the polyatomic anion. If the polyatomic anion’s name ends in “‐
ate”, then the acid’s name ends in “‐ic.” If the polyatomic anion’s name ends in “‐ite”,
then the acid’s name ends in “‐ous.”
Rules for Naming Hydrates
Hydrate: a crystalline compound with a specific number of water molecules chemically
combined
Anhydrous: “without water” Heating a hydrate causes the weakly bonded water
molecules to evaporate
1. Use the naming rules for ionic compounds to name the first part
2. Use a molecular prefix to indicate the number of water molecules attached
3. End the name with “hydrate”
Feb 15­1:56 PM
Chemical Bonding
Chemical Bond: a mutual electrical attraction between nuclei and valence e‐ of different
atoms. The type of bond depends on e‐ configuration and electronegativity. Atoms combine
to become more stable (lower potential energy)
Types of bonds
1. Ionic: an electrostatic force of attraction between cations and anions
2. Covalent: sharing of e‐ pairs between atoms
1. nonpolar covalent: equal sharing of e‐
2. polar covalent: unequal sharing of e‐
3. Metallic: an attraction between metal atoms and outer, mobile e‐
Feb 15­1:57 PM
Naming and Bonding Notes.notebook
February 16, 2016
Octet Rule: Atoms tend to gain/lose/share e‐ so that they have 8 valence e‐
Exceptions: H (2e‐)
Be (4e‐)
B (6e‐)
Some elements have expanded octets (more than 8 valence e‐) due to empty or
available “d” orbitals
Determining Bond Character from Electronegativities
Subtract electronegativities to find bond character between atoms
0 nonpolar
0% covalent
Electronegativity difference
0.3
polar
1.7
5%
covalent
50%
Percent Ionic Character
ionic
3.3
100%
Feb 15­1:57 PM
Ionic Bonding
Ionic Bond: formed by an electrostatic force of attraction between cations and anions.
The total (+) charge must equal the total (‐) charge. Metals (+) bond with nonmetals (‐).
Formula Unit: simplest combining ratio of ions in a compound; does not exist
independently
Properties of Ionic Compounds:
High melting points
Most are soluble in water
Crystalline solids
Hard solids, but will fracture along planes
Poor conductors in solids for, but good in aqueous or liquid state
Feb 15­2:10 PM
Naming and Bonding Notes.notebook
February 16, 2016
Covalent Bonding
Molecular Compound: neutral compound consisting of covalently bonded nonmetals
Molecule: smallest representative unit of a molecular compound. It can exist
independently.
Diatomic Molecules: elements that exist as two atoms covalently bonded together.
H2, O2, F2, Br2, I2, N2, Cl2
“HOFBrINCl”
Nonpolar Molecule: equal distribution of shared e‐ Example: H2 à
H:H
Polar Molecule: unequal distribution of shared e‐ resulting in (+) and (‐) poles called
“dipoles”
Example: H2O
electronegativity of O = 3.5 δ‐
electronegativity of H = 2.2 δ+
Bond length: average distance between nuclei of 2 bonded atoms (sum of atomic radii)
Bond angle: angle between 2 bonds in a molecule
Bond energy: energy needed to break a bond and form neutral atoms. As bond length increases,
bond energy decreases. As electronegativity difference increases, bond energy increases (more
ionic character).
Properties of Molecular Compounds
fairly weak bonds
Low melting points
Brittle, dull solids or gases
Poor conductors
Feb 15­2:11 PM
Metallic Bonding
Metallic Bond: an attraction of metallic atoms for delocalized e‐. Positive metal atoms in
a “sea” of e‐.
Due to overlapping empty “p” and “d” orbitals, outer e‐ roam freely from one atom
to another.
The strength of a metallic bond is determined by the number of outer e‐
The strongest metals are transition metals‐ some “d” e‐ can delocalize.
Softer metals are combined with harder metals to form alloys.
Properties of Metallic crystals
Good Conductors
Shiny (luster)
Hard solids
High mp
Malleable
Ductile
Feb 15­2:12 PM
Naming and Bonding Notes.notebook
Molecular Geometry
February 16, 2016
“Shape”
Molecular Polarity: the distribution of charge, equal (nonpolar) or unequal (polar)
Depends on: 1) bond polarity and
1. molecular shape
Molecular polarity influences intermolecular forces (imf’s)
VSEPR Theory: Valence Shell Electron Pair Repulsion
Electron pairs (clouds) will spread as far apart as possible to minimize repulsive forces
U = unshared pair
S = shared pair
U‐U > U‐S > S‐S
Repulsive forces
Feb 15­2:12 PM
Shape
Bond Angle
Bonded to
central atom
Unshared e‐
pairs
example
Linear
180°
2 atoms
0
HCl
2 bonds
0
CO2
2
1
2
2
H2O
120°
3
0
BH3
108°
3
1
NH3
109.5°
4
0
CH4
Bent
Trigonal
planar
Trigonal
pyramidal
Tetrahedral
105°
Feb 15­2:13 PM
Naming and Bonding Notes.notebook
February 16, 2016
Molecular Polarity
Nonpolar molecules are usually symmetrical.
Polar molecules are usually asymmetrical.
Polar molecules are called dipoles; have (+) and (‐) ends.
If you need to know if a molecule is polar; ask yourself 2 questions: Is it Asymmetrical? And, Are
there non‐bonding central atom electrons (lone pairs). If the answer to either or both of these
questions is “Yes” then your molecule is polar. If neither is true, then you have a nonpolar
molecule.
Physical Properties are often a result of Molecular Geometry/Polarity.
Feb 15­2:13 PM