Naming Compounds
Chemical Bonding: The force that holds two atoms together is called a chemical bond. This bond may be
formed many different ways but for now we will only discuss two types of bonds, ionic and covalent. An
element’s properties and behavior depends on their valence electrons. These outer electrons are also responsible
for how atoms bond to another.
Formation of Positive Ions: Groups 1, 2, and 13 will lose electrons to achieve stable octets. This process is
favourable because it requires far less energy than gaining multiple electrons.
Formation of Negative Ions: Group 15, 16, and 17 have greater attraction to electrons and thus try to gain
more electrons to get a stable octet.
Polyatomic Ions: A group of atoms that have a charge. For example, OH- (hydroxide).
Naming with Only One Type of Atom:
To name anything with only one type of atom just use the name that appears on the periodic table of elements.
However, there are some exceptions to this rule.
1. There are 7 diatomic elements which include H2, N2, O2, F2, Cl2, Br2, and I2. These elements are found in
nature bonded to each other. These still use the names given in the periodic table.
2. Monatomic cations use the element name followed by the word ion.
Ex. Cs+ is named cesium ion.
3. Monatomic Anions take their name from the root of the element plus the “ide” suffix. All anions can also be
found on your reference sheet.
Ex. Br- is named bromide ion.
4. Phosphorous is found in nature in a group of 4 (P4) but is still named phosphorous.
Practice- Name the following Atoms:
Li
Br2
Tc
Ca 2+
P4
Rn
S2Titanium
Sodium ion
Phosphide ion
Naming with One Type of Atom Practice:
a)Cr
b) Sn
c) Bismuth
d) Mercury
e) S2f) Cs+
g) B3+
h) Mg2+
i) Ij) Hk) chloride ion
l) lithium ion
m) Oxide ion
n) hydrogen ion
o) Nitride ion
Naming Ionic Compounds
Ionic Bonds: These bonds are formed when ions are joined due to electrostatic attraction. Typically a metal and
a non-metal form ionic bonds. For example, sodium transfers an electron to chlorine gas and forms sodium
chloride. If an ionic bond occurs between a metal and oxygen it is an oxide (Fe2O3). Most other ionic bonds are
salts. The number of electrons lost must equal the number of electrons gained and the overall charge must equal
zero.
So if calcium bonds with fluorine, there must be 2 fluorine atoms to take 1 electron each. Likewise if sulfur
bonds with sodium, there must be two sodium atoms to give each sulfur atom 1 electron.
Naming Binary Ionic Compounds (Non-metal and metal):
FORMULA
1. Write the symbol of the metal or positive ion first.
2. Write the symbol of the negative ion. Common negative ions and nonmentals are listed on your reference
sheet.
3. Overall charge must equal 0. Aluminum chloride is written as AlCl3 not AlCl.
Al3+
Mn4+
Co3+
Cu2+
Pb4+
ClO2IN3FORMULA TO NAME
1. Write the name of the positive ion followed by the name of the negative ion.
Ex. MgO is named magnesium oxide, Na2S is named sodium sulfide.
NaOH is named sodium hydroxide
2. Common negative ions and nonmentals are listed on your reference sheet. Take these names as they are! DO
NOT change them.
Ex. Fluorine becomes fluoride and bromine becomes bromide.
3. Many transition metals on the periodic table have more than one possible charge, and therefore when we look
at an ionic compound that contains a multivalent metal, we need to be able to identify the charge of the metal
ion. If the metal forms more than one type of cation, the charge has to be indicated using roman numerals.
Roman Numerals
One (I)
Five (V)
Two (II)
Six (VI)
Three (III)
Seven (VII)
Four (IV)
Eight (VIII)
2+
Ex. Fe becomes Fe (II) and Fe3+ becomes Fe (III).
If we have a formula of FeCl2 which of the following would be the correct name?
iron (II) chloride
OR
iron (III) chloride
Practice – Name the following ionic compounds:
NaCl: sodium chloride (also known as table salt)
AlBr3: aluminum bromide
NiO: nickel (II) oxide
PdI4: palladium (IV) iodide
PbCl2: lead (IV) chloride
Name to Formula
1. Write the name of the cation. Use the roman numerals to predict the charge of each atom.
Remember, the Roman numeral is used to help identify the charge of the atoms.
2. Write the name of the anion as shown on your reference sheet.
Practice – Write the formula of the following ionic compounds:
Sodium oxide: Na2O
Potassium chloride: KCl
Scandium nitride: ScN
Cobalt (III) sulfide: Co2S3
Naming Ionic Bonds with a Polyatomic Ion:
Formula to Name:
1. If the polyatomic compound is the cation then use the name found on your reference sheet
Ex. Ammonium (NH4+)
2. If the polyatomic compound is the anion find the name on your reference sheet. Use that name and do not
change the ending. When using an ion there must be brackets around the entire ion if there is more than one of
that ion.
Ex. Magnesium cyanate is written as Mg(OCN)2 NOT as MgOCN2
Ex. ClO3- (chlorate)
3. Again, the charges must equal 0. If they do not you must balance them. Remember, the polyatomic ion is a
compound hooked together which means you must use brackets around the term to balance it.
Ex. Magnesium nitrate is written as Mg(NO3)2
Al3+
H30+
NH4+
Co3+
Cu2+
Pb4+
SCNSO42PO42S2O32-
Al(SCN)3
Al2(SO4)3
Al2(PO4)3
Al2(S2O3)3
H3OSCN
(H3O)2SO4
(H3O)2PO4
(H3O)2S2O3
NH4SCN
(NH4)2SCN
(NH4)2PO4
(NH4)2S2O3
Co(SCN)3
Co2(SO4)3
Co2(PO4)3
Co2(S2O3)3
Cu(SCN)2
CuSO4
CuPO4
CuS2O3
Pb(SCN)4
Pb(SO4)2
Pb(PO4)2
Pb(S2O3)2
Practice – Name the following ionic bonds with polyatomic ions:
NaC2H3O2: sodium acetate
H2O2: hydrogen peroxide
K2HPO4: potassium hydrogen phosphate
Pt(CrO4)2: platinum (IV) chromate
Ca(BrO2)2: magnesium bromite
NaOH: sodium hydroxide
H3OBr: hydronium bromide
Name to Formula:
1. Write the name of the cation. Use the roman numerals to predict the charge of each atom.
Remember, the Roman numeral is used to help identify the charge of the atoms.
2. Write the name of the anion as shown on your reference sheet.
Practice – Write the formula of the following ionic compounds:
Sodium dihydrogen phosphate: Na2H2PO4
Cesium permanganate: CsMnO4
Ammonium sulfide: (NH4)2S
Zinc thiocynate: Zn(SCN)2
Naming Covalent Molecules
Covalent Bonds: The second type of bond is a covalent bond. These bonds occur when both atoms need
electrons to get to a stable octet. Instead of transferring electrons they share them. These usually occur with a
non-metal and a non-metal. For example, F has an electron configuration of 1s22s22p5 which means it has 7
valence electrons and must gain one more to achieve a full octet. It achieves this by sharing with another
fluorine atom to form F2.
It is important to note that some compounds require more than one covalent bond to achieve an octet, like N2 or
O2. Because these compounds share electrons NO CHARGES are associated with each atom in the compound.
Naming Covalent Compounds (Non-metal and Non-metal):
Formula to Name:
1. The element farthest to the left of the periodic table is named first. If they are in the same column then the
one with the most protons is named first.
2. Add the appropriate prefix to the front name (unless the prefix is mono-). This is used to indicate the number
of atoms in each compound. Mono- is not used if there is only one atom of the first element.
Ex. CO2 is named carbon dioxide NOT monocarbon dioxide (mono is not used on the first element)
B3Br is name triboron monobromide (mono is used on the second one)
**Prefixes found on reference sheet.
3. The second uses a prefix and add an “ide” to the ending of the name.
Ex. Tetrachloride
Practice – Name the following covalent compounds:
CO3: carbon trioxide
SF6: sulfur hexafluoride
CO: carbon monoxide
As2O3: diarsenic trioxide
IF5: iodine pentafluoride
N2O4: dinitrogen tetraoxide
Name to Formula:
Use the rules above in order to predict the formula:
Dichlorine monoxide: Cl2O
Silicon dioxide: SiO2
Dicarbon trioxide: C2O3
Carbon monofluoride: CF
Pentanitrogen trioxide: N5O3
Heptacarbon trinitride: C7N3
Octaoxygen dinitride: O8N2
Naming Hydrates
Formulas with a ●H2O
These are compounds that have water molecules bonded to them to create a more stable structure. The stable
structure may be required to ship the compound from place to place safely.
1. Use the previous rules to name the compound.
2. Attach ●H2O (named hydrate) to the end of the compound with the appropriate prefix to indicate the number
of water molecules.
Ex. NaNO3●3H2O is named sodium nitrate trihydrate
Pb(NO3)2 ●5H2O is named lead(II) nitrate pentahydrate
Practice – Name the following compounds containing hydrates:
CaCl2●6H2O: calcium chloride hexahydrate
Co(NO3)2●6H2O: cobalt (II) nitrate hexahydrate
Cu(NO3)2●3H2O: copper (II) nitrate trihydrate
Practice – Use the same rules to predict the formula:
Ammonium sulfide heptahydrate: (NH4)2S●7H2O
Iron (II) silicate pentahydrate: FeSiO3 ● 5H2O
Lead (IV) nitrate octahydrate: Pb(NO3)4 ● 8H2O
Copper (II) chloride trihydrate: CuCl2 ● 3H2O
Gold (III) hydride pentahydrate: AuH3 ● 5 H2O
Naming Acids
Naming Binary Acids (Hydrogen and 1 Other Element):
To name the compound first determine the ending of the root element:
Rule #1 –If the anion’s name ends with “-ide”:
o Add the prefix “hydro –.”
o Replace the “-ide” ending with “-ic”.
o Follow the name with the word acid.
Rule #2 –If the anion’s name ends with “-ite”:
o Replace the “-ite” ending with “-ous”.
o Follow the name with the word acid.
Rule #3 –If the anion’s name ends with “-ate”:
o Replace the “-ate” ending with “-ic”.
o Follow the name with the word acid.
Ex. HBr is named hydrobromic acid
HIO3 is named iodic acid
HCrO3 is named chromous acid
HCl is named hydrochloric acid
HCN is name hydrocyanic acid
Practice – Name the following binary acids:
HIO3: iodic acid
HF: hydrofluoric acid
H3PO3: phosphorous acid
H2CO3: carbonic acid
H2Cr2O7: dichromic acid
H2Se: hydorselenic acid
Give the formula of the following acids:
Nitrous acid: HNO2
Hyrdoselenic acid: H2Se
hydrosulfuric acid: H2S
Chromic acid: H2CrO4
Selenous acid: H2SiO3