Formula Writing and Naming Compounds in General Chemistry

1. Let’s Review!
Can you still recall about the
rules in naming ions?

2. Naming Ions
Positive Ion (cation)
The name of the ion is the SAME as the name of the
element.
Mg+2 magnesium ion
Na+ sodium ion
Negative Ion (anion)
Get the root name of the element and add the suffix
“ide”
O-2 oxide ion
Cl- chloride ion

3. Learning Objectives
At the end of the session, the learners
are expected to name compounds
given their chemical formulas and
write formulas given the names of
the compounds.

4. Formula Writing and Naming
Compounds

5. Guide Questions
How are chemical formulas written?
How are molecules represented?
How do you name compounds?

6. Writing Formulas from the Names of
Inorganic Compounds
To write the formula of a given compound,
write the positive ion on the first term in
the name, and the negative ion on the
second term. Then, do the criss-cross
and express the result in simplest ratio.

7. Examples
Magnesium chloride : Mg+2 Cl- formula is MgCl2
1 2
Plumbic oxide : Pb+4 O-2 formula is PbO2
2 4 2
Sodium sulfate : Na+ SO4
-2 formula is Na2SO4
2 1
Calcium carbonate : Ca+2 CO3
-2 formula is CaCO3
2 2

8. Naming of Inorganic
Compounds

9. Binary Compound
The term binary means “two”.
A binary compound is a compound in
which only two elements are present.

10. Types of Binary Compounds
There are two types of binary compounds: ionic
and molecular.
An ionic compound is a combination of a metal
and nonmetal while a molecular compound
consists of two nonmetals.

11. Ionic Compound
To name a binary compound of a metal
(with a fixed positive charged number)
and a nonmetal, write the unmodified
name of the metal followed by the name
of the nonmetal (modified to end in ide).

13. Ionic Compound
Examples:
MgCl2 ------------ magnesium chloride
BaS ------------ barium sulfide
Al2O3 ------------ aluminum oxide
KBr ------------ potassium bromide

14. Give the name of the following
compounds:
1. MgF2
2. AlN
3. LiBr
4. Na2O
5. Sr3P2
Magnesium fluoride
Aluminum nitride
Lithium bromide
Sodium oxide
Strontium phosphide

15. A binary compound of a metal (with more than one
charged number) and a nonmetal can be named:
By using the suffix –ous for the positive
element with lower charged number and the
suffix –ic for the positive element with higher
charged number.
FeCl2 ----------- ferrous chloride
FeCl3 ----------- ferric chloride
Cr2S3 ----------- chromic sulfide
CrS ----------- chromous sulfide

16. By using Roman numeral following the name
of the metal to indicate its charged number.
Examples:
FeCl2 ---------- iron(II) chloride
FeCl3 ---------- iron(III) chloride
Sn3P4 ---------- tin(IV) phosphide
AuCl ---------- gold(I) chloride

17. Give the name of the following
compounds:
1. CuO
2. Cu2S
3. MnO2
4. HgO
5. PbBr4
cupric/copper(II) oxide
cuprous/copper(I) sulfide
manganic/manganese(IV) oxide
mercuric/mercury(II) oxide
plumbic/lead(IV) bromide

18. Molecular Compound
To name a binary compound of two nonmetals, a prefix is
used to indicate the number of atoms for both names except
for mono- in the first name.
Examples:
NO ---------- nitrogen monoxide
N2O3 ---------- dinitrogen trioxide
P2S5 ---------- diphosphorus pentasulfide
Cl2O7 ---------- dichlorine heptaoxide

19. Give the name of the following
compounds:
1. Cl2O
2. P2S5
3. SI6
4. XeF4
5. HCl
dichlorine monoxide
diphosphorus pentasulfide
sulfur hexaiodide
xenon tetrafluoride
hydrogen chloride

20. Exceptions
B2H6 diborane
CH4 methane
SiH4 silane
NH3 ammonia
PH3 phosphine
H2O water
H2S hydrogen sulfide

21. Binary Acid
Binary acid (compound of H and a nonmetal)
is named by using the prefix hydro- and the
suffix –ic attached to the names of the acid-
forming nonmetal.
Examples:
HCl ---------- hydrochloric acid
HBr ---------- hydrobromic acid

22. Give the name of the following
binary acids:
1. HF
2. HI
3. H2S

23. Ternary Compound
A ternary compound is composed of
three or more kinds of elements.

24. Ternary Compound
The naming of ternary compounds follows the
same rule as that of the binary ionic
compound: the name of the cation is given
first, followed by the name of the anion.
Examples:
NaNO3 ---------------------- sodium nitrate
BaCrO4 ---------------------- barium chromate
K2SO3 ---------------------- potassium sulfite

25. Give the name of the following
ternary compounds:
1. FeSO4
2. Na2CO3
3. Ca3(PO3)2

26. Ternary Acid
Ternary acids or oxyacids are those containing
H, O and the acid-forming element. In naming a
ternary acid, the ending -ous is used instead of
-ite and -ic instead of -ate.
Examples:
HClO ---------- hypochlorous acid
HClO3 ---------- chloric acid
H2SO3 ---------- sulfurous acid
H2SO4 ---------- sulfuric acid

27. Give the name of the following
ternary acids:
1. H2CO3
2. HC2H3O2
3. H3PO4
4. HCN

28. Evaluation ( ¼ sheet of paper)
In a 10-minute time, give the names of the compounds given
their formulas and give the formulas given their names:
1. AlP
2. NiCl4
3. Zn(OH)2
4. Cl2O7
5. H2S (in water)
6. Iodine heptafluoride
7. Boric acid
8. Calcium chlorate

29. Assignment
Study your lesson in preparation of
your summative test very soon.