A.P. Chemistry Chapter Three Outline
Chemical Compounds
I.
Molecular Compounds: atoms of two or more different elements combined
A. Molecular Formulas: represent kinds of elements and amounts of atoms.
Example: FeCl3 indicates one atom of iron and three of chlorine
Organic Compounds: all contain carbon, usually also hydrogen, often
oxygen, nitrogen, sulfur, and halogens.
Inorganic Compounds: do not contain carbon or carbon and hydrogen
B. Structural Formulas: show how atoms within a molecule are connected
C. Condensed Formulas: emphasize the atoms or groups of atoms connected
to each carbon atom; for example CH3CH2OH
II.
Naming Binary Inorganic Compounds
A. Binary molecular compounds consist of molecules that contain atoms of
only two elements.
1. For hydrogen containing compounds containing oxygen, sulfur,
and the halogens, the hydrogen is listed first and the second
element’s ending is changed to-ide.
Example: HCl = hydrogen chloride
HF = hydrogen fluoride, etc
III.
Hydrocarbons: organic compounds composed of only carbon and hydrogen
atoms
A. General Formula: CnH2n+2 where n is a whole number.
Example: propane has three carbons and 2(3) + 2 = 8 hydrogens
B. Naming: First four need to be memorized (try molly eats peanut butter
pies) for methane, ethane, propane, butane and pentane. From pentane on, the
name is the root word for the number of carbon atoms, ending with –ane.
Example: for eight carbons: eight = oct- (think octagon) + ane so octane
IV.
Alkanes and their Isomers
A. Isomers: two or more compounds that have the same molecular formula
but different arrangements of the atoms
1. Constitutional, or structural isomers, have the same molecular
formula but differ in the order in which the atoms are bonded
together.
CH2=C-CH2-CH3
|
CH3
2-methyl-1-butene
CH2=CH-CH-CH3
|
CH3
3-methyl-1-butene
B. Straight-Chain and Branched Chain Isomers of Alkanes
In a straight chain, all carbons are attached in a straight line. In a branched
chain not all carbons are attached in a straight line.
V.
Ions and Ionic Compounds
An ionic compound is composed of positive and negative ions.
Cation = positive ion. The quantity of electrons lost is equal to the positive charge.
Anion =negative ion. The quantity of electrons gained is equal to the negative charge.
A. Metals tend to lose electrons to form positive ions
B. When non-metals react with metals they tend to gain electrons to form negative
ions.
Example: if iron reacts with sulfur: Iron will lose electrons, forming a positive ion
Fe2+ and sulfur will gain an electron forming S2They come together to form FeS.
C. Using the periodic table to predict charges:
1. Group 1 elements form +1 ions. Except Hydrogen which can also form -1
2. Group 2 elements form +2 ions
3. Group 3 elements usually form +3 ions
4. Group 6 elements form –2 ions
5. Group 7 elements form –1 ions
6. Group 8 doesn’t form ions
7. the rest all vary
8. Transition elements often form +2 or +3. When an ion has two possible
charges, such as iron (II) (Fe2+) and iron (III) (Fe3+) it is named with the
ending –ous for the lower charge and –ic for the higher charge (ferrous
and ferric in this case)
D. Polyatomic ions: a unit of two or more atoms that have a net charge. Memorize
these! See page 91.
E. Ionic Compounds: an ionic compound is made because cations and anions are
attracted to each other by electrostatic forces – the forces of attraction between
positive and negative charges.
1. Coulomb’s law: the attraction between oppositely charged ions increases
with charge and decreases with the distance between the ions
where q1 and q2 are the magnitudes of the charges, d is the
distance, and k is a constant.
F. How to predict if a compound will be ionic:
1. metal + non-metal = ionic compound
2. metal + metal(s) = molecular compound
3. metal + polyatomic ion composed of nonmetals= ionic compound
G. Writing Formulas for Ionic Compounds: the cation symbol is written first,
followed by the anion symbol. Remember compounds are electrically neutral so
the overall charge is zero.
VI.
Properties of Ionic Compounds
A. Cystal Lattice: in ionic solids, cations and anions are held in an orderly
arrangement so that each cation is surrounded by anions and each anion is
surrounded by cations.
B. Formula unit: The formula of an ionic compound indicates only the
smallest whole number ratio of the number of cations to the number of
anions in the compound.
C. Characteristic Properties: high melting points and distinctive crystalline
shapes.
1. the higher the charges, the higher the melting point. Thus PO43will have a higher melting point than Cl-.
2. Crystals can only vibrate so they don’t conduct electricity as
solids
VII.


Electrolytes: Ionic Compounds in Aqueous Solutions
Most ionic compounds are soluble (will dissolve) in water
When an ionic compound dissolves in water it dissociates (breaks into
charged ions). For example, when NaCl is dissolved it breaks into Na+ ions
and Cl- ions.
Electrolytes are substances that conduct electricity when dissolved in water.
Aqueous ionic compounds are electrolytes because the ions are free to move
about
Most molecular compounds that are water soluble continue to exist as
molecules when dissolved and do not conduct electricity. These are called
nonelectrolytes.


VIII.
Moles of Compounds
A. Molar mass is the mass of one mole of a substance. The molar mass in
grams per mole is also called the molecular weight of a compound.
B. Formula weight is the term for the molar mass or molecular weight of an
ionic compound and is equal to the sum of all the atoms in the compounds
formula.
C. Gram . Mole Conversions: to convert from grams to moles divide by the
molar mass; to convert from moles to grams multiply by the molar mass.
D. Ionic Hydrates: Ionic compounds that have water molecules trapped
within their crystal lattice. The trapped water is called the water of
hydration. Example: CuSo45H2O has 5 moles of water associated with
every mole of copper (II) sulfate. This is called copper (II) sulfate
pentahydrate.
IX.
Percent Composition
A. Mass Percent or Percent Composition
The mass percent of an element is equal to its formula weight divided by the
compounds formula weight, multiplied by 100.
Example: the mass percent of carbon in carbon dioxide is roughly
12(12+16+16) = .27 repeating times 100 = 27.27%
X.
Determining Empirical and Molecular Formulas
 One can determine the formula of a compound from its mass percent data
A. Empirical Formula: the simplest possible ratio of atoms in a molecule
 Remember the subscripts in a formula indicate the relative number of moles of
each element in one mole of that compound (hence there are two moles of
hydrogen and one mole of oxygen in one mole of water, H2O).
A. to go from mass percent to empirical formula:
First Divide mass percent by molar mass.
Example: you know the mass percent of a compound is 78.13% Boron and
21.87 % Hydrogen. That means that in 100 grams of the compound, there are
78.13 grams of Boron and 21.87 grams of hydrogen.
78.13 g B x (1 mole B/10.811g) = 7.227 mole Boron
21.87 g H x (1 mole H/1.008 grams) = 21.70 mole Hydrogen
Second, divide larger amount of moles by smaller
21.70 moleH/7.227 mole H = 3.003 mole H/1mole B
This tells you that there are three moles of Hydrogen for every mole of Boron,
giving you the empirical formula BH3.
B. Molecular Formula: the actual formula of a compound. The molar mass
of the molecular compound needs to be experimentally determined. For
example, in the compound that contains only boron and hydrogen, one
mole is experimentally determined to have a mass of 27.67grams. The
mass of BH3, however only has a mass of 13.84 grams. You divide the
experimentally determined formula weight by the empirical weight. The
result is to be multiplied by each element in the compound.
Example: 27.67/13.84 = 2. So the molecular compound is B2H6.
XI.
The Biological Periodic Table: Of the periodic table, about 30 of the elements
are necessary for life.
XII. The Dietary Minerals – there are 28
Major minerals (more than 100 mg per kg of body)and trace elements (we need small
amounts)
XIII.
Biomolecules: Carbohydrates and Fats
A. Carbohydrates: have the general formula Cx(H2O)y. For example, when x
and y = 6 you have C6H12O6 (glucose)
1. Monosaccharides: simple carbohydrates, contain one sugar unit.
Fort example, glucose.
2. disaccharides: two monosaccharides connected. Sucrose, for
example is a sucrose molecule connected to a glucose molecule
3. polysaccharides: many (up to thousands) of monosaccharides
connected in a chain.. Cellulose is an example.
B. Fats and Oils: three fatty acid molecules joined to a glycerol
molecule. This combination is a triglyceride.