1. Lecture 39 – Lecture 40 Naming Molecules Ozgur Unal
NIS – CHEMISTRY
Lecture 39 – Lecture 40
Naming Molecules
Ozgur Unal

2. Naming Compounds Many molecular compounds have common names:
H2O  water
CH3COOH  vinegar
All molecular compounds have scientific names:
CO2  Carbon dioxide
H2SO4  Sulfuric acid
We will learn the rules to name binary molecular compounds, binary acids and oxyacids.
Binary molecular compounds are composed of only two nonmetal atoms, such as H2S, CO2, N2O.
Acids (binary and oxy-) contain covalent bonds, this is why we study them here.

3. Naming Binary Molecular Compunds
Rules for naming binary molecular compounds:
1- The first element in the formula is always named first, using the entire element name.
2- The second element in the formula is named using its root and adding the suffix –ide.
3- Prefixes are used to indicate the number of atoms of each element that are present in the compound  Table 8.3.
Example:
N2O3  dinitrogen trioxide
SCl2  Sulfur dichloride

4. Naming Binary Molecular Compunds
There are exceptions to using the prefixes in step 3:
The prefix mono- in the first element in the compound is never used  Carbon dioxide (CO2)
If using a prefix results in two consecutive vowels, one of the vowels is usually dropped  Dinitrogen pentoxide (N2O5)
Example: Name the following compounds
a) P2O5 b) SO2 c) NF3 d) CCl4
a) diphosphorus pentoxide b) sulfur dioxide
c) nitrogen trifluoride c) carbon tetrachloride

5. Naming Binary Molecular Compunds
Example: Write the formula for the following compounds
diarsenic trioxide
dihydrogen monoxide
phosphorus pentachloride
a) As2O3
b) H2O
c) PCl5

6. Naming Binary Acids
Water solutions of some molecules are acidic, and are named as acids.
If a compounds produces H+ in solution, it is an acid.
Example: HCl
A binary acid contains hydrogen and one other element.
The rules for naming binary acids:
1- The first word has the prefix hydro- to name the hydrogen part of the compound. The rest of the first word consists of a form of the root of the second element plus the suffix -ic.
2- The second word is always acid.
Example: HCl  Hydrochloric acid.

7. Examples: HI  Hydroiodic acid H2S  Hydrosulfuric acid
Naming Binary Acids
Examples:
HI  Hydroiodic acid
H2S  Hydrosulfuric acid
If an acid does not contain oxygen, even if it is not a binary acid, these two rules can be used to name them.
The root of the second part of the name is the root of the polyatomic ion that the acid contains.
Example: HCN is composed of Hydrogen (H) and Cyanide (CN)
HCN  Hydrocyanic acid

8. Naming Oxyacids
An acid that contains both a hydrogen atom and an oxyanion is referred to as an oxyacid.
Rules for naming an oxyacid:
1- First, identify the oxyanion present. The first word of an oxyacid’s name consists of the root of the oxyanion and the prefix per- or hypo- if it is part of the name, and a suffix. If the oxyanion’s name ends with the suffix –ate, replace it with the suffix –ic. If the name of the oxyanion ends with the suffix –ite, replace it with the suffix –ous.
2- The second word of the name is always acid.
Example: HNO3  Nitric acid
Example: HNO2  Nitrous acid

9. Examples: HClO3  ? HClO2  ? H2SO4  ? H2SO3  ?
Naming Oxyacids
Examples:
HClO3  ?
HClO2  ?
H2SO4  ?
H2SO3  ?
HClO3  Chloric acid
HClO2  Chlorous acid
H2SO4  Sulfuric acid
H2SO3  Sulfurous acid

10. Writing Formulas From Names
Write the formulas for the following molecules:
Silver chloride
Dihydrogen monoxide
Chlorine trifluoride
Diphosphorus trioxide
Carbonic acid
Hydrochloric acid
Dicarbon tetrahydride
Hydrobromic acid
Sulfurous acid
Bromous acid
Sulfuric acid
AgCl
H2O
CF3
P2O3
H2CO3
HCl
C2H4
HBr
H2SO3
HBrO2
H2SO4