UNIT 7 REVIEW
Ionic & Covalent Bonds
Ionic Bonding (transfer of electrons)
– Some atoms gain electrons to become anions
– Others lose electrons to become cations
– Ions are attracted by their opposing charges
• Electrical neutrality maintained
–
–
–
–
Crystal Lattice structure
High Melting & Boiling points
Good conductors of heat & electricity
Not easily crushed
Covalent Bonding (sharing of electrons)
– Electrons share electrons to fill incomplete shells
– Most Important Bonding in Organic Materials (and Organisms)
– Low Melting & Boiling points (volatile – evaporates easily)
– Poor conductors of heat & electricity
– Easily crushed
Metallic Bonding
A. Outermost electrons wander freely through metal. - “Sea of Electrons”
B. Free electrons can move rapidly in response to electric fields, hence metals
are a good conductor of electricity.
C. Free electrons can transmit kinetic energy rapidly, hence metals are good
conductors of heat.
• Ductile - can be drawn into wires
• Malleable - can be hammered into shapes
Chemical Formulas and
Chemical Compounds
Chemical Names & Formulas
• Significance of chemical formulas:
– Gives relative number of atoms of each kind
of element.
– Subscripts: small numbers to the right that
tell the number of atoms
– If no subscript then it is understood to be 1
– H2SO4
– 2 hydrogens, 1 sulfur, 4 oxygen
Chemical Names & Formulas
• When parentheses are used you must
multiply inside and out.
–Al2(SO4)3
(2 Aluminums, 3 Sulfurs, 12 Oxygens)
Names of Binary Compounds
• Binary compounds are those formed
from only 2 elements.
• To write their formulas the positive ion is
written first and then the negative.
• To name them use the complete name of
the positive ion and add the negative ion
name but change the ending to “-ide.”
(Sulfur becomes sulfide, oxygen becomes
oxide, phosphorous becomes phosphide)
Formulas of Binary Compounds
• To write the formula of a
compound you must consider the
charges and multiply by adding
subscripts so that the overall
charge on the compound is zero.
• Ex: zinc is (2+) and sulfur is (2-) so:
– ZnS
– Name: Zinc Sulfide
Formulas of Binary Compounds
• Ex: zinc is (2+) and iodine is (1-)
so:
2+ 2- ( = 0 )
– Zn 2+ I 1Subscripts1
2
– ZnI2
– Name: Zinc Iodide
Formulas of Binary Compounds
• How do you know the charge?
– Use the valence electrons
– Group 1 = 1+, Group 2 = 2+, 3+, 4±
– Group 15 = 3-, Grp. 16 = 2-, Grp. 17 = 1– May use ion chart for transition metals.
Stock System of Nomenclature
• Some transition metals have more than
one possible charge:
• Ex. Copper: Cu+ and Cu2+
Iron:
Fe2+ and Fe3+
Lead:
Pb+3 and Pb+4
Tin:
Sn+2 and Sn+4
Stock System of Nomenclature
• The charges of these elements must be
represented in the name of the
compounds.
• Charges are provided by using Roman
numerals in the names
• Ex: Iron (II) oxide and Iron (III) oxide
• Formulas: FeO
Fe2O3
Stock System of Nomenclature
• How do you know how to write the formula???
• Iron (II) combines with oxygen
Fe2+ O2-
(charges equal zero so FeO)
• Iron (III) combines with oxygen
Fe3+ O2- (add subscripts and multiply
2
3
to equal zero
Stock System of Nomenclature
• How do you know how to write the name if
you only see the formula???
• CuBr2
• The name is Copper Bromide but is it
Copper (I) Bromide or Copper (II)
Bromide???
Stock System of Nomenclature
Then +1
If charges are
+1
-2 ≠ 0
-1
Cu Br2
Stock System of Nomenclature
Then +2
If charges are
+2
-2 = 0
-1
Cu Br2
Naming Binary Molecular Compounds
• Molecular compounds are those in which
the elements are close together on the
periodic table.
• Ex:
– Nitrogen and Oxygen
– Carbon and Oxygen
– Sulfur and Oxygen
– Phosphorus and Chlorine
Naming Binary Molecular Compounds
• Ex: Compounds of Nitrogen and Oxygen
– N2O
– NO
– NO2
– N2O3
– N2O5
• traditional method uses prefixes.
Section 1:
Naming Binary Molecular Compounds
Prefixes indicate the number of atoms in the
compound
•
•
•
•
•
•
•
•
•
•
1 atom: Mono
2 atoms: Di
3 atoms: Tri
4 atoms: Tetra
5 atoms: Penta
6 atoms: Hexa
7 atoms: Hepta
8 atoms: Octa
9 atoms: Nona
10 atoms:Deca
Section 1:
Naming Binary Molecular Compounds
• The less electronegative element is written first
and is given a prefix only if it has more than one
atom in the formula.
• Next element has a prefix indicating the number
of atoms and ends typically with “ide.”
• Examples:
–
–
–
–
–
N2O
NO
NO2
N2O3
N2O5
Dinitrogen Monoxide
Nitrogen Monoxide
Nitrogen Dioxide
Dinitrogen Trioxide
Dinitrogen Pentoxide
Compounds with Polyatomic Ions
• Many compounds are composed of
polyatomic ions (a group of covalently
bonded atoms that carry a charge).
• Examples of polyatomic ions:
– Sulfate (SO4)2– Nitrate (NO3) –
– Phosphate (PO4)3– Carbonate (CO3)2– Hydroxide (OH) – Ammonium (NH4)+
Section 1:
Compounds with Polyatomic Ions
• Most polyatomic ions end with “–ate” or “ite” but there are a few exceptions:
–Cyanide (CN)–Hydroxide (OH)-
Note of caution:
Don’t confuse these with binary
compounds since they end in “ide.”
Naming Compounds with Polyatomic Ions
• Simply write the complete name of the
positive element and the name of the
polyatomic ion.
• KNO3 = Potassium Nitrate
• CaSO4 = Calcium Sulfate
• Al(OH)3 = Aluminum Hydroxide
Writing Compounds with Polyatomic Ions
• Writing the formulas for these compounds
are a little trickier.
• Make sure that you treat the polyatomic ion
as a whole unit and do not change its
subscripts!
• (SO4)2- = 1 sulfate ion
• (SO4)2-2 = 2 sulfate ions NOT…
(S2O8)
Writing Compounds with Polyatomic Ions
• Examples:
• Potassium nitrate
Totals: 1+
Charges: +
Symbols: K
Final Formula:
and 1= 0
(NO3)
KNO3
(no parenthesis needed since only 1 ion is required
Writing Compounds with Polyatomic Ions
• Examples:
• Aluminum Sulfate
Totals:
6+
3+
Charges:
Symbols: Al
Add Subscripts:
2
Final Formula:
and
(SO4)
62-
= 0
3
Al2(SO4)3
(parenthesis must be used to show 3 sulfate ions)
Writing Compounds with Polyatomic Ions
• Polyatomic ions may be paired with
transition metals that have multiple
charges.
• Ex: Copper (II) and sulfate = CuSO4
• But Copper (I) and sulfate = Cu2SO4
• When naming them the Roman numeral
must be included.
• Fe3(PO4)2 = Iron (II) Phosphate
Naming Acids and Salts
• Memorize the formulas for the common
acids.
• All begin with one or more H atoms.
– Sulfuric Acid H2SO4
– Hydrochloric Acid HCl
– Nitric Acid HNO3
– Phosphoric Acid H3PO4
– Carbonic Acid
H2CO3
Organic Molecules
Name based on number of
Carbons
A series of prefixes are used to designate the
number of carbon atoms in a carbon chain
meth
1C
hex
6C
eth
2C
hept
7C
prop
3C
oct
8C
but
4C
non
9C
pent
5C
dec
10 C
30
Suffixes on the end of the name of an
organic molecule tell you what major
family the molecule belongs to
The suffix for an alkane is “-ane”
all single bonds
“saturated” with hydrogen
The suffix for an alkene is “-ene”
contains a double bond
“unsaturated”
CnH2n+2
CnH2n
Parent and suffix…
• The parent is named based on the
number of carbons
• 1 carbon = “meth”
• So a one-carbon alkane is called
methane
CH4
Parent and suffix…
• 2 carbons = “eth”
• So a two carbon alkane is called ethane.
C2H6
a two carbon alkene is called
ethene
C2H4
Parent and suffix…
• 3 carbons = “prop”
• So a three carbon alkane is called
propane.
C3H8
a three carbon alkene is called propene
C3H6
Parent and suffix…
• 4 carbons = “but”
• So a four alkane is called butane.
C4H10
a four carbon alkene is called butene
C4H8