Chemical Names and
Formulas
Unit 5
Counting Atoms
 The
subscript tells how many of that
element is present.
 Eg: H2O2= 2 hydrogen, 2 oxygen
 If there is no subscript next to the
symbol, it counts as “1”.
 Eg: NaCl = 1 sodium & 1 chlorine
Counting Atoms
 If
the subscripted number is outside
of the parenthesis, it is distributed to
all elements within the parenthesis.
 Eg: Ca(NO3)2 = NO3 x 2.
 A preceeding coefficient is multiplied
to all atoms in the compound.
 Eg: 2NaCl = 2 sodium & 2 chlorine
Counting Atoms
 Calcium
Carbonate: CaCO3.
Ca = Calcium =
1
C = Carbon =
O = Oxygen =
1
3
Total atoms =
5
Counting Atoms
 Magnesium
Hydroxide: Mg(OH)2.
Mg = Magnesium =
H = Hydrogen
O = Oxygen
Total atoms
1
=
=
2
2
=
5
Counting Atoms
 Acetic
Acid: 2HC2H3O2.
H = Hydrogen
=
2+6=8
C = Carbon
O = Oxygen
=
=
4
4
Total atoms
=
16
 Now
complete the Counting Atoms
review worksheet.
Chemical Formulas
 The
simplest compounds contain 2
elements and are called Binary.
 In ionic binary compounds, a cation
 IMPORTANT: ALL COMPOUNDS ARE
and an anion join together to form a
NEUTRAL!!!
neutral compound.
 Ionic compounds are made from a
metal and a non-metal.
Ionic
Cation + Anion =
Compound
Chemical Formulas
 Potassium
Bromide = KBr
 Calcium Bromide = CaBr2
 Lithium Fluoride = LiF
 Lithium Oxide = Li2O
 Note that the subscript has nothing
to do with the name of the ionic
compound.
Chemical Names
 Example:
LiF
 The element with the positive charge,
cation (the metal) is written first.
 This element is given its usual name, in
this case, Lithium.
 The second element is the anion. It’s
name will be changed to end in “-ide”.
Fluorine is changed to Fluoride.
 The compound’s name = Lithium
Fluoride.
Chemical Formula for
Potassium Bromide
 Write
the two symbols for the ions in
the compounds, placing the symbol
for the cation first.
K
+1
 Determine
Br
-1
KBr
the charge of each ion
Balanced!
from the
oxidation state on the
 If
the charges
periodic
table. are equal, drop them
and write the formula.
Calcium Bromide
 If
the charges are not equal, “lasso”
the number only (not the sign) to
write the formula.
Ca
 After
+2
Br
-1
CaBr2
seeing
more examples,
NOT Balanced!
complete practice problems 1-10 on
your worksheet.
Transition Elements and Roman
Numerals
 Some
metals can form more than
one type of ion and therefore, have
more than one possible charge.
 To tell which charge is used, the
chemical name contains a Roman
numeral.
 The Roman numeral tells the
charge of the cation.
Transition Elements and Roman
Numerals
Roman
numerals are
NEVER used in the
chemical formula!!
Rules to Write a Chemical Formula
when Roman Numerals are Present
 To
write the chemical formula for
Iron (III) Sulfide:
 Write the two symbols for the ions in
the compounds, placing the symbol
- 22
+3
for the
Fe2S3
Fe cationS first.
 Get the charge of the metal from the
Roman numeral in ( ) after the metal
and look up the anion’s charge.
Rules to Write a Chemical Name
when Roman Numerals are Needed
 If
the metal has more than one
oxidation state, the chemical name
will contain a Roman numeral.
Oxygen
has using
a
 Now write the chemical
name
a
 Start
with
the
anion
to
determine
its
Mn must
can
have
havea
charge
of -2
 You
CANNOT
lasso
up
to
determine
roman
numeral
to(VI)
represent
Manganese
Oxide
charge
a
charge
of
of
+7,
+6
and
there the
are 3
overall
negative
charge.
the
Roman
numeral.
6,
to
4,
neutralize
2
or
3
for a total
charge of the Manganese.
the -6 charge.
MnO3
charge of -6.
Let’s Try Again
 Write
the chemical name of Fe2O3.
The 2 Fe ions
canan
mustFe
have
have
a
Rust
overall
charge
charge
of
of +6.
So 6/2
+2 or 3
= +3.
Fe2O3
Oxygen has a
charge of -2
and there are 3
for a total
charge of -6.
Iron (III) Oxide
 Now write the chemical name.
 Now do part C of your worksheet.
Polyatomic Ions in Names
 The
cation keeps its name.
CaCO3
Calcium
 The
Carbonate
Made of more than
one element so it
is aalso
polyatomic
ion
keeps
ion.
polyatomic
its
name, even though it is an anion.
Polyatomic Ions in Formulas
Barium Phosphate
 We
recognize Phosphate as a
polyatomic ion because it ends in
“ate”.
 Get the charge of the polyatomic ion
from the chart.
 Use the periodic table for the charge
on your element.
Barium Phosphate

Lasso!

Let’s
Write
Add
NO!!
Are the
each
thecharges
chemical
ion’s charge.
balanced?
symbols.
+ 22
Ba
 We
-3
3
PO4
have 2 “PO4” ions so we need
parentheses Ba
to 3separate
(PO4)2 the ion from
the extra subscript.
Let’s Try Again
 Write
the formula for Magnesium
Hydroxide.
Mg
 We
+2
OH
- 11
have 2 “OH” ions so we need
parentheses Mg(OH)
to separate the ion from
2
the subscript.
 Now do part D of your worksheet.
Covalent Compounds
 Covalent
compounds are made from
2 non-metals and are binary.
 Since there are no ions involved, we
don’t look at charges.
 The subscript to the right of the
element tells the prefix to use for
that element.
 SO2 = Sulfur Dioxide
Covalent Compound Prefixes
 Mono
= one
 Di = two
 Tri = three
 Tetra = four
 Penta = five
 Hexa
= six
 Hepta = seven
 Octa = eight
 Nona = nine
 Deca = ten
Triangle
Hexagon
Some Covalent Compounds
NF3
nitrogen trifluoride
N2Cl4
dinitrogen tetrachloride
NO2
nitrogen dioxide
N2O
 Now
TOXIC!
dinitrogen monoxide
do part E of
your worksheet.
Laughing Gas
Naming Acids
 Acids
= compounds that give off
hydrogen ions when dissolved in
water.
 Acids begin with H.
 Acids will always have some H next to
an anion.
 The anion determines the name.
Binary Acids
 Binary
Acids contain only 2 elements,
the cation being hydrogen. Add the
prefix hydro-, take the anion name
and change the suffix -ide to –ic.
 HCl(aq)
Hydrochloric Acid
 HF(aq)
Hydrofluoric Acid
 HI(aq)
Hydroiodic Acid
Binary Acids
 Exceptions:
 HCN
= Hydrocyanic Acid
CN = Cyanide
 HN3 = Hydroazoic Acid
azo = Nitrogen
Oxyacids
 Ternary
Acids contain 3 elements,
hydrogen, oxygen and one other
element (a polyatomic ion).
 The suffix is determined by the
number of oxygens.
 If the anion ends in -ate, change the
suffix to –ic acid.
HNO3 = Hydrogen & Nitrate =
Nitric Acid
More Oxyacids
H2SO4
=
Hydrogen & Sulfate =
Sulfuric Acid
HClO3 =
Hydrogen & Chlorate =
Chloric Acid
More Oxyacids
 If
the anion has one less oxygen & ends
in -ite, change the suffix to –ous acid.
HNO2 = Hydrogen & Nitrite =
Nitrous Acid
H2SO3
Hydrogen & Sulfite =
=
Sulfurous Acid
HClO2 =
Hydrogen & Chlorite =
Chlorous Acid
Name these Acids
 HF
 H3P
 H3PO4
 H3PO3
 HCN
 H2CrO4
 Hydrofluoric
Acid
 Hydrophosphic Acid
 Phosphoric Acid
 Phosphorous Acid
 Hydrocyanic Acid
 Chromic Acid
Oxyacids
 If
a third acid is formed with fewer
oxygens than -ite, it is given the
prefix hypo- and the suffix –ous.
 E.g. HClO = Hydrogen &
hypochlorite = Hypochlorous Acid
 If it has one more oxygen than -ate,
it is given the prefix per- and the
suffix –ic.
 E.g. HClO4 = hydrogen & perchlorate
= Perchloric Acid.
Writing Formulas for Acids
 Hydrogen
will always be first.
 The name tells you the anion.
 Make sure the molecule is neutral.
 If the name starts with the prefix
hydro- and ends with -ic, there is no
oxygen in the formula.
 If there is no prefix, the suffix –ate
comes from –ic and –ite comes from
–ous.
Write Formulas for these Acids
 hydroiodic
 acetic
acid
acid
 carbonic acid
 phosphorous acid
 hydrobromic acid
 HI
 HC2H3O2
 H2CO3
 H3PO3
 HBr
Naming Organic Compounds
 Hydrocarbons
are compounds made
of only carbon and hydrogen linked
in long chains.
 Alkanes – have single bonded
carbons so they are saturated.
Naming Organic Compounds
 Alkenes
– have double bonded
carbons so they are unsaturated.
 Alkynes – have triple bonded carbons
 We’ll work with alkanes so
hydrocarbons will have the suffix –
ane.
Organic Stems
1 carbon = meth-
6 carbons = hex-
2 carbons = eth-
7 carbons = hept-
3 carbons = prop-
8 carbons = oct-
4 carbons = but-
9 carbons = non-
5 carbons = pent-
10 carbons = dec-
Organic Compounds
 If
the atoms are linked in a ring
rather than in a chain, the prefix
cyclo- is added.
 Hexane in a chain
CH3-CH2- CH2- CH2- CH2- CH3.
 Cyclohexane has 6 carbons in a ring.
Each point represents
a carbon.
Organic Compounds
 If
the chain is straight:
CnH2n+2
n=#carbons
 E.g. C3H(2×3)+2 = C3H8 = Propane
 CH3-CH2-CH3
 If the chain is cyclic:
CnH2n
 E.g. C3H6 = cyclopropane