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CHEM 1411 General Course Guide - Lab

Flowchart of Overall Strategy for Naming Chemical Compounds

An overall strategy for naming chemical compounds.
The rules for naming binary compounds can be found in the box below named Naming Compounds.

Naming Compounds

Examples of the rules for naming binary ionic compounds
Compound Ions Present Name
NaCl Na+, Cl- Sodium chloride
KI K+, I- Potassium Iodide
CaS Ca2+, S2- Calcium sulfide


Li+, N3- Lithium nitride
CsBr Cs+Br- Cesium bromide
MgO Mg2+, O2- Magnesium oxide

Binary compounds: 
Compounds composed of two elements.

The first type we will consider is ionic compounds.
Binary ionic compounds: Contain a cation (+ ion) that is ALWAYS written first in the formula and an anion (- ion).

Ionic compound: Metal + Nonmetal(s)

Rules for Naming Type I Binary Compounds

  1. The cation is ALWAYS named first and the anion second.
  2. A monatomic cation takes its name from the name of the element (e.g., Na+ = sodium for compounds containing this ion).
  3. A monatomic anion is named by taking the root of the element name and adding -ide (e.g., Cl- = chloride).


Helpful Tip: The illustration below shows the general trend for ionic charges

Common Monatomic Cations and Anions
Cation Name Anion Name







































Formulas From Names:

The compound needs to be neutral. This means that you need to get the charges to balance out.

Let's look at the above example of Lithium nitride.

The ions are: Li+  and   N3-

The nitrogen ion contains a 3- charge while lithium has a 1+ charge. The three from the charge of nitrogen is going to become the subscript of lithium and lithium's 1 is going to become the subscript to nitrogen. This is called the criss-cross method and the final product will look like this:

Now, you can see that there are 3 lithiums to the 1 nitrogen to balance out the charges and make the compound neutral. Since the nitrogen shows in the formula, the 1 is not needed and that is why you don't see it. 

What about magnesium oxide (MgO)?

Both of those ions contain 2:  Mg2+, O2-

But from the above information, the formula should look like this: Mg2O2
The lowest ratio is needed, and for this example, the lowest ratio is 1:1. The twos will cancel out to leave 1 and give us the final product of:


This video by Tyler DeWitt gives more detailed instructions on how to write ionic formulas

Practice: Highlight the text inside the box to reveal answer

Problems Answers (Highlight boxes) Reasons (Highlight boxes)

Sodium bromide

NaBr Sodium = Na+ and bromine = Br- 
By using the criss-cross method, the 1 from Na will become the subscript of Br
The 1 from the Br will become the subscript of Na.
GaAs Gallium arsenide Ga = Gallium (stays the same)
As = arsenic   Remove -ic and add -ide for arsenide
KCl Potassium chloride K = Potassium (stays the same)
Cl = Chlorine  Remove -ine and add -ide for chloride
Aluminum sulfide Al2S3 Aluminum = Al3+ and sulfur = S2-
The 3 from the Al will become the subscript of S
The 2 from S will become the subscript of Br
You must have 2 Al and 3 S to balance the charge and make the compound neutral
Mg3P2 Magnesium phosphide Mg = Magnesium (stays the same)
P = Phosphorous Remove -orous and add -ide
Lithium oxide Li2O Lithium = Li+ and Oxygen = O2-
The 1 from Li will become the subscript of O
The 2 from O will become the subscript of Li
You must have 2 Li to balance the charge of O
CaBr Calcium bromide Ca = Calcium (stays the same)
Br = Bromine Remove the -ine and add -ide
Barium sulfide BaS Barium = Ba2+ and Sulfur = S2-
After using the criss-cross method, you are left with Ba2S2
The 2's are the same and become the lower ratio which is 1:1
Final answer is BaS
NaF Sodium fluoride Na = Sodium (stays the same)
F = Fluorine  Remove the -ine and add -ide
MgCl2 Magnesium chloride Mg = Magnesium (stays the same)
Cl = Chlorine Remove -ine and add -ide
Sodium nitride Na3N Sodium = Na+ and Nitrogen = N3-
The 1 from Na is going to become the subscript of N
The 3 from N is going to become the subscript of Na
You must have 3 Na to balance out the charge of N.
Common Type II Cations
Ion Systematic Name
Fe3+ Iron(III)
Fe2+ Iron(II)
Cu2+ Copper(II)
Cu+ Copper(I)
Co3+ Cobalt(III)
Co2+ Cobalt(II)
Sn4+ Tin(IV)
Sn2+ Tin(II)
Pb4+ Lead(IV)
Pb2+ Lead(II)
Hg2+ Mercury(II)


Ag+ Silver
Zn2+ Zinc
Cd2+ Cadmium
The mercury(I) ions ALWAYS occur bound together to form Hg22+ ions. Although silver, zinc, and cadmium are transition metals, they form only one type of ion and a Roman numeral is not used.

In this section, you will come to find out that there are metals that have more than one type of positive ion and can form more than one type of ionic compound with a given anion.

Iron is a good example. Iron can be: Fe2+ or Fe3+
These will be written as: iron(II) and iron(III)

Helpful Tip:
Roman numerals are required to help specify which ion is being used. Elements that form only one cation DO NOT need to be identified by a Roman numeral.

FUN FACT: There is another system for naming these ionic compounds. The lower charged ion will have the ending -ous while the higher charged ion will have the ending -ic . So, iron will be written as: ferrous ion and ferric ion


This video by Tyler DeWitt teaches you how to name ionic compounds that have transition metals in them.


Table for Naming Binary Ionic Compounds
Does the compound contain Type I or Type II cations?
Type I Type II
Name the cation using the element name. Using the principle of charge balance, determine the cation charge.
  Include in the cation name a Roman numeral indicating the charge.

Helpful Tip:
Silver, zinc, and cadmium only have ONE type of ion even though they are transition metals. This means that they don't need Roman numerals when their name is being written.

Practice Problems: Highlight boxes for answer
Problems Answers: Highlight boxes to reveal Reasons: Highlight boxes to reveal
Titanium(III) bromide TiBr3 Titanium = Ti3+ and Bromine = Br-
Use the criss-cross method, the 3 from Ti will become the subscript for Br
The 1 from Br will become the subscript for Ti
You need 3 Br to balance the charge of Ti
Tin(IV) selenide SnSe2 Tin= Sn4+ and Selenium = Se2-
The 4 from Sn will become the subscript for Se
The 2 from Se will become the subscript for Sn
Sn2Se4 is not the lowest ratio. If you divide by two, the final answer is
Co2O3 Cobalt(III) oxide You can tell that the subscripts are the lowest ratio because
the 2 subscript came from O which is O2- (the number didn't change)
So, when you reverse the criss-cross method, the 3 
subscript from O returns as Co charge giving you Cobalt(III)
Oxygen Remove -ygen and add -ide
V2S5 Vanadium(V) sulfide Sulfur = S2-
By looking at Vanadium's subscript, you can see that the 2 is still there.
When you reverse the criss-cross method, vanadium will have a charge
of 5 and you will have Vanadium(V) in your answer
Sulfur Remove -ur and add -ide
Copper(I) oxide Cu2O Copper = Cu+ and Oxygen = O2-
The criss-cross method - The 1 from Cu becomes the subscript for O
The 2 from O becomes the subscript for Cu
Pb3N2 Lead(II) nitride Nitrogen = N3-
Pb's subscript is 3 which means that the numbers haven't changed
Reverse the criss-cross method and the 2 subscript becomes the
charge of Pb to give you Lead(II) in your answer
Nitrogen Remove -ogen and add -ide
AgBr Silver Bromide Silver only has one type of ion and does not need Roman numerals
Bromine Remove -ine and add -ide
Titanium (II) selenide TiSe Titanium = Ti2+ and Selenium = Se2-
Criss-cross to give Ti2Se2
Divide by 2 to obtain the lowest ratio and answer is TiSe
SnS2 Tin(IV) sulfide Sulfur = S2-
Notice that Sn does not have a subscript. It should be 2 since S has a 
charge of 2
This means that the lowest ratio is being used.
If you multiply each subscript by 2, then the S subscript will give you 4 and
you will have Sn2S4.
Reverse criss-cross and you will have Tin(IV) as your answer
Sulfur Remove -ur and add -ide

For more practice problems and a video tutorial, view Tyler DeWitt's Naming Ionic Compounds with Transition Metals Practice Problems

For even further help, visit the Name-inator website.

Common Polyatomic Ions
Ion Name Ion Name
Hg22+ Mercury(I) NCS- or SCN- Thiocyanate
NH4+ Ammonium CO32- Carbonate
NO2- Nitrite HCO3- Hydrogen Carbonate
(Bicarbonate is a widely used common name)
NO3- Nitrate ClO- or OCl- Hypochlorite
SO32- Sulfite ClO2- Chlorite
SO42- Sulfate ClO3- Chlorate
HSO4- Hydrogen Sulfate (bisulfate a widely used common name) ClO4- Perchlorate
OH- Hydroxide C2H3O2- Acetate
CN- Cyanide MnO4- Permanganate
PO43- Phosphate Cr2O72- Dichromate
HPO42- Hydrogen Phosphate CrO42- Chromate
H2PO4- Dihydrogen Phosphate O22- Peroxide
    C2O42- Oxalate
    S2O32- Thiosulfate


Polyatomic Ion: An ion containing a number of atoms

Oxyanions: Anions containing an atom of a given element and different numbers of oxygen atoms

  • When there are two members in a series:
    • The name with the smaller number of oxygen atoms will end in -ite
    • The name with the larger number of oxygen atoms will end in -ate

SO32- = sulfite and SO42- = sulfate

  • When there are more than two members in a series:
    • The fewest oxygen atoms will have the prefix hypo-
    • The most oxygen atoms will have the prefix per-

ClO- = hypochlorite and ClO4- = perchlorate


Helpful Tip:



This video by Tyler DeWitt teaches you how to write formulas for ionic compounds that contain polyatomic ions.

Practice Problems: Highlight boxes to reveal answers
Problems Answers: Highlight boxes Reasons: Highlight boxes
Ammonium chloride NH4Cl Ammonium = NH4+ and Chlorine = Cl-
Use the criss-cross method,
The 1 from NH4 becomes the subscript for Cl
The 1 from Cl becomes the subscript for NH4
Iron(III) nitrate Fe(NO3)3 Iron(III) = Fe3+ and Nitrate = NO3-
Use the criss-cross method
The 3 from Fe becomes the subscript of NO3
Notice that NO3 is in parentheses, you're not adding the subscripts. T
hey are separate.
You have 3 oxygens for the nitrate and now 3 nitrates for the compound.

The 1 from nitrate becomes the subscript for Fe

Cr(PO4)2 Chromium(VI) phosphate Phosphate has a charge of 3- (PO43-)
Cr has no subscript from PO43- which means that the formula now is on
the lowest ratio
Multiply the subscripts by 3 to get the regular subscripts back giving
Cr a subscript of 3 and PO4 a subscript of 6
Reverse criss-cross - Cr has a charge of 6 to write Chromium(IV)
V(CO3)2 Vanadium(IV) carbonate Carbonate has a charge of 2- (CO32-)
V has no subscript and that means that the formula is on the lowest ratio
Multiply the subscripts by 2 to get the regular subscripts back giving
V a subscript of 2 and CO3 a subscript of 4
Reverse criss-cross - V has a charge of 4 to write Vanadium(IV)
Scandium(III) hydroxide Sc(OH)3 Scandium(III) = Sc3+ and Hydroxide = OH-
Use the criss-cross method
The 1 from OH becomes the subscript of Sc
The 3 from Sc becomes the subscript of OH
Remember to put OH in parenthesis because this shows you have
3 OH instead of just 3 H
Strontium acetate Sr(C2H3O2)2 Strontium = Sr2+ and Acetate = C2H3O2-
Use the criss-cross methodd
The 1 from C2H3O2​ becomes the subscript of Sr
The 2 from Sr becomes the subscript of C2H3O2
Remember to use parenthesis on C2H3O2to show that you have 2
Ag3PO4 Silver phosphate Silver only has one type of ion and does not need a Roman numeral.
Ag = Silver
PO4 = Phosphate
KMnO4 Potassium permanganate K = Potassium
MnO4 = Permanganate
Cadmium sulfite CdSO3 Cadmium = Cd2+ and Sulfite = SO32-
Use criss-cross method
The 2 from SO3 becomes the subscript of Cd
The 2 from Cd becomes the subscript of SO3
You should have Cd2​(SO3)2 but you can make the subscript smaller
Divide by 2 and obtain the lowest ratio to get final answer of CdSO3

For more practice problems on naming compounds and writing formulas, visit Mr. Carman's Blog Chemical Compounds Practice Quiz.

Prefixes Used to Indicate Number in Chemical Names
Prefix Number
mono- 1
di- 2
tri- 3
tetra- 4
penta- 5
hexa- 6
hepta- 7
octa- 8
nona- 9
deca- 10

Binary Covalent Compounds: Formed by two nonmetals

  • These compounds do not contain ions

Naming Binary Covalent Compounds

  1. ​The first element in the formula is named using the full element name.
  2. The second element is named as if it were an anion.
  3. The prefixes are used to indicate the numbers of atoms present.
  4. The prefix mono- is never used for naming the first element.

CO = Carbon monoxide NOT monocarbon monoxide

Helpful Tip:
If the element begins with a vowel, the final or of the prefix is dropped. Carbon monoxide NOT carbon monooxide. Dinitrogen tetroxide NOT dinitrogen tetraoxide.

Examples of naming covalent compounds
Compound Systematic Name Common Name
N2O Dinitrogen monoxide Nitrous oxide
NO Nitrogen monoxide Nitric oxide
NO2 Nitrogen dioxide  
N2O3 Dinitrogen trioxide  
N2O4 Dinitrogen tetroxide  
N2O5 Dinitrogen pentoxide  




 Some compounds are just always referred to by their   common name.


​ H2O = Water
 NH3 = Ammonia
 H2O2 = Hydrogen Peroxide



This video by Tyler Dewitt teaches you how to write names for Covalent Molecular Compounds.

Practice Problems: Highlight boxes to reveal answers.
Problems Answers
CO2 Carbon dioxide
SCl2 Sulfur dioxide
diphosphorus pentoxide P2O5
CCl4 Carbon tetrachloride
tricarbon tetranitride C3N4
selenium difluoride SeF2
B2H6 diboron hexahydride
nitrogen tribromide NBr3
S3N2 trisulfur dinitride
Se3S6 triselenium hexasulfide

For more practice problems on naming compounds and writing formulas, visit Mr. Carman's Blog Chemical Compounds Practice Quiz.


Acid: A molecule in which one or more H ions are attached to an anion.

The rules for naming acids depend on whether the anion contains oxygen.
If the name of the anion ends in -ide, the acid is named with the prefix hydro- and the suffix -ic.

HCl = Hydrochloric acid

When the anion contains oxygen, the acidic name is formed from the root name of the anion with a suffix of -ic or -ous.

  1. If the anion name ends in -ate the suffix -ic is added to the root name.
    • H2SO4 = contains the sulfate anion (SO42-) and is called sulfuric acid
    • HC2H3O2​ = contains the acetate ion (C2H3O2-) and is called acetic acid
  2. If the anion name ends in -ite, then -ous is used.
    • H2SO3​ = contains the sulfite anion (SO32-) and is called sulfurous acid
    • HNO2​ = contains the nitrite anion (NO2-) and is called nitrous acid

Application of Acid Rules

Acid Anion Name
HClO4 Perchlorate Perchloric acid
HClO3 Chlorate Chloric acid
HClO2 Chlorite Chlorous acid
HClO Hypochlorite Hypochlorous acid

This video by Tyler DeWitt will teach you how to look at the chemical formula for an acid and then write its name.

Names of Non-Oxygen-Containing Acids (aqueous solutions)
Acid Name
HF Hydrofluoric acid
HCl Hydrochloric acid
HBr Hydrobromic acid
HI Hydroiodic acid
HCN Hydrocyanic acid
H2S Hydrosulfuric acid
Name of Some Oxygen-Containing Acids
Acid Name
HNO3 Nitric acid
HNO2 Nitrous acid
H2SO4 Sulfuric acid
H2SO3 Sulfurous acid
H3PO4 Phosphoric acid
HC2H3O2 Acetic acid











For more practice problems on naming compounds and writing formulas, visit Mr. Carman's Blog Chemical Compounds Practice Quiz.
For more practice problems and a video tutorial, view Tyler DeWitt's Naming Acids Practice Problems.