Transcript AP Chemistry Notes

AP Chemistry Notes
Molecules, Ions, & Inorganic
Nomenclature
Molecules and Molecular Compounds:
 A molecule consists of two or more
atoms bound together.
H2
H2O
NH3
CH4
Molecules & Chemical Formulas:
 Each molecule has a chemical formula.
 The chemical formula indicates:
 Which atoms are found in the molecule, and
 In what proportion they are found.
 Compounds composed of molecules are
molecular compounds.
These contain at least two types of atoms.
 Different forms of a compound which have
different chemical formulas are known as
allotropes.

• Allotropes differ in their chemical and physical properties.
Molecular & Empirical Formulas:
 Molecular formulas –
 Give the actual numbers and types of atoms in a
molecule.
• Examples: H2O2; C6H12O6; N2H4
 Empirical formulas –
 Give the relative numbers and types of atoms in a
molecule (they give the lowest whole-number ratio
of atoms in a molecule).
• Examples: HO; CH2O; NH2
Picturing Molecules:
 Molecules occupy three-dimensional space.
 However, we often represent them in two dimensions.
 The structural formula gives the connectivity between individual
atoms in the molecule.
 If the structural formula does not show the shape of the
molecule, then either a perspective drawing, ball-and-stick
model, or space-filling model is used.
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

Perspective drawings use dashed lines and wedges to represent
bonds receding and emerging from the plane of the paper.
Ball-and-stick models show atoms as contracted spheres and the
bonds as sticks. The angles in the ball-and-stick model are
accurate.
Space-filling models give an accurate representation of the relative
sizes of the atoms and the 3D shape of the molecule.
Picturing Molecules:
Ions and Ionic Compounds:
 If electrons are
added or removed
from a neutral atom,
an ion is formed.
Remember…
ELECTRONS are
gained and lost …
nothing happens
to the protons!
Ions and Ionic Compounds:
 When an atom or molecule loses electrons, it
becomes positively charged.

Positively charged ions are called cations.
 When an atom or molecule gains electrons, it
becomes negatively charged.

Negatively charged ions are called anions.
 In general, metal atoms tend to lose electrons
and nonmetal atoms gain electrons.
 When molecules lose electrons, polyatomic
ions are formed.
Predicting Ionic Charges:
 An atom or molecule can lose more than one
electron.
 Many atoms gain or lose enough electrons to
have the same number of electrons as the
nearest noble gas (group 18).
 The number of electrons an atom loses is
related to its position on the periodic table.
Predicting Ionic Charges:
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
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
Group 1  +1
Group 2  +2
Group 13  +3
Group 14  +4 / -4
Group 15  -3
Group 16  -2
Group 17  -1
Group 18  STABLE
Ionic Compounds:
 A great deal of chemistry involves the transfer of
electrons between species.
 In general, ionic compounds are usually
combinations of metals and nonmetals, whereas
molecular compounds are generally composed of
nonmetals only.
 Writing formulas for ionic compounds:



You need to know the ions of which it is composed.
The formula must reflect the electrical neutrality of the
compound.
You must combine cations and anions in a ratio so that the
total positive charge is equal to the total negative charge.
Ionic Compounds:
Nomenclature:
 Inorganic binary compounds
 Ionic & covalent bonds
 Compounds composed of two elements
Nomenclature:
 Binary ionic compounds (type 1)
 Cation written first
• Monatomic cation named from element

Anion second
• Monatomic anion named from the root of the element and
changing the ending to -ide
Nomenclature:
 Binary ionic compounds (type 2)
 When cations form more than one type of
positively charged ion, the charge on the ion is
indicated by Roman numerals
• Example – iron (III) & iron (II)

ALSO – for metals with only two ions – the ion with
the higher charge ends in –ic and the ion with the
lower charge ends in –ous
• Example – ferric & ferrous (aka: iron)
Nomenclature:
Nomenclature:
 Binary covalent compounds
 First element in the formula is named first using
the full element name

Second element is named like anions (root of
element & -ide)

Prefixes are used to denote numbers of atoms
present in the compound
• Exception: mono- is not used with the first element
Nomenclature:
 Prefixes:
Mono- = 1
 Di- = 2
 Tri- = 3
 Tetra- = 4
 Penta- = 5
 Hexa- = 6
 Hepta- = 7
 Octa- = 8
 Nona- = 9
 Deca- = 10

Nomenclature:
 Another exception:
 Some binary covalents are referred to by
their common names NOT their systemic
names
• Examples: water, ammonia, phosphine…
Nomenclature:
Nomenclature:
 Ionic compounds with polyatomic ions
 Polyatomic names aren’t changed when
naming compounds
 Oxyanions
can vary in the number of
oxygen atoms composing the polyatomic
ion
• With variation - name changes BUT CHARGE
DOES NOT CHANGE
Nomenclature:
 When there are two possible oxyanions, most
oxygen atoms ends in –ate & fewest oxygen
atoms ends in –ite
 When there are more than two possible
oxyanions:
Most oxygen atoms also ends in –ate AND it is
given the prefix per Fewest oxygen atoms also ends in –ite AND it is
given the prefix hypo
Nomenclature:
 Examples:
 Sulfate (SO42-) & sulfite (SO32-)
(ClO4-), chlorate (ClO3-),
chlorite (ClO2-), & hypochlorite (ClO-)
 Perchlorate
Nomenclature:
 Acids
 Acids w/oxyanions
• Acid name formed from the root of the anion
name and the ending is –ic or –ous depending
on whether the oxyanion is an –ate or an –ite
– ate becomes –ic & -ite becomes -ous
 Acids
w/o oxyanions
• The prefix hydro- is used and the ending of the
anion is -ic
Nomenclature:
Mixed Practice
1.
2.
3.
4.
5.
6.
7.
8.
9.
Dinitrogen monoxide
Potassium sulfide
Copper (II) nitrate
Dichlorine heptoxide
Chromium (III) sulfate
Ferric sulfite
Calcium oxide
Barium carbonate
Iodine monochloride
1.
2.
3.
4.
5.
6.
7.
8.
9.
N2O
K2S
Cu(NO3)2
Cl2O7
Cr2(SO4)3
Fe2(SO3)3
CaO
BaCO3
ICl
Mixed Practice
1.
2.
3.
4.
5.
6.
7.
8.
9.
BaI2
P4S3
Ca(OH)2
FeCO3
Na2Cr2O7
I2O5
Cu(ClO4)2
CS2
B2Cl4
1.
2.
3.
4.
5.
6.
7.
8.
9.
Barium iodide
Tetraphosphorus trisulfide
Calcium hydroxide
Iron (II) carbonate
Sodium dichromate
Diiodine pentoxide
Cupric perchlorate
Carbon disulfide
Diboron tetrachloride
Nomenclature:
 A HYDRATE is an salt that has water
molecules trapped within its crystals.
 Every hydrate has a certain number of water
molecules associated with each formula unit
of the ionic compound. The number of water
molecules is indicated by using prefixes.

Mono- for one; di- for two; tri- for three; etc.
Hydrate Examples:
 WRITING FORMULAS:
copper(II) fluoride tetrahydrate
CuF2 ·4 H2O
calcium nitrate trihydrate
Ca(NO3)2 ·3 H2O
 WRITING NAMES:
MgSO4 · 7 H2O
magnesium sulfate heptahydrate
FeCl2 · H2O
iron (II) chloride monohydrate
Nomenclature:
Nomenclature:
 Complex Ion Formation:
 IUPAC Rules for Naming Coordination
Compounds –
• 1. The cation is always named before the anion, with a
space between the names.
• 2. In naming a complex ion, the ligands are named
before the metallic ion.
• 3. Ligands have special endings.
– Notice that an –o ending is used in place of any –ide
ending for anions.
– For anions ending in –ate, the –o is substituted for the –e.
– For neutral ligands, the name of the molecules is used,
with the exception of H2O, NH3, CO, and NO.
Nomenclature:
• 4. Ligands are named first, in alphabetical order, followed
by the metal name.
– The Greek prefixes (di = 2, tri = 3, tetra = 4, penta = 5,
hexa = 6, etc.) are used to denote the number of simple
ligands present.
– For more complicated ligands, the prefixes bis (twice), tris
(thrice), tetrakis (four times), pentakis (five times), and
hexakis (six times) are used.
– NOTE: Prefixes do not affect the alphabetical order
• 5. Many metals exhibit variable oxidation numbers.
– The oxidation number of the metal is designated by a
Roman numeral in parentheses following the name of the
complex ion or molecule.
– The Roman numeral is omitted if a metallic cation does not
exhibit variable oxidation numbers.
• Example: Silver is always +1 in a compound or
complex ion, so no Roman numeral is used.
Nomenclature:
• 6. For anionic complex ions (those having negative charges),
the suffix –ate is added to the name of the metal. The English
name for the metal is used, except in the following cases where
the Latin name is used to identify the metal. The suffix –ate
indicates that the complex ion is an anion. Neutral and cationic
complexes do not use suffixes.
Latin Names for Some Metal Ions Found in Anionic Complex Ions:
Copper
Cuprate
Gold
Aurate
Iron
Ferrate
Lead
Plumbate
Silver
Argentate
Tin
Stannate
Nomenclature:
• 7. In the case of complex-ion isomerism, the
names cis or trans may precede the formula of
the complex ion name to indicate the spatial
arrangement of the ligands.
– Cis means the ligands occupy adjacent coordination
positions
– Trans means opposite positions
Nomenclature:
 Examples:
 [Cr(H2O)4Cl2]+ = tetraaquodichlorochromium(III)
 [Cr(H2O)2Cl4]- = diaquotetrachlorochromate(III)
 K2[CoCl4] = potassium tetrachlorocobaltate(II)
 Na[Al(OH)4] = sodium tetrahydroxoaluminate
 [Zn(NH3)4]Cl2 = tetraamminezinc chloride
 [Pt(NH3)4][PtCl6] = tetraammineplatinum(II)
hexachloroplatinate(IV)