Chemistry is involved with various and diverse interactions of matter either around us or simply inside the laboratory. These are described using the language of chemistry which consists of symbols, formulas and equations.

1. Prof. Liwayway Memije-Cruz

2. Introduction
Chemistry is involved
with various and
diverse interactions of
matter either around
us or simply inside
the laboratory. These
are described using
the language of
chemistry which
consists of symbols,
formulas and
equations.

3. Chemical Symbols
 shorthand
abbreviations for
elements
composed of a
single capital
letter or a capital
letter and one or
two small letters.

4. Chemical Formula
 indicates the relative number of atoms of each element
in a substance. It consists of symbols of elements and
subscripts which give the number of atoms of each
element.

5.  In writing formulas, the total positive charges
plus the total negative charges must equal to
zero since the compound is electrically neutral.

6. Cations, anions, radical or polyatomic ions

7. Rules in writing formulas of compounds
 There are basic rules in writing formulas of compounds. These are:
Write first the symbol of the positive ion followed by the symbol of
the negative ion or radical. A radical or polyatomic ion is a group of
atoms which acts as a single atom.
Criss-cross: the valence of the positive ion becomes the subscript of
the negative ion, while the valence of the negative ion becomes the
subscript of the positive ion. (You have to disregard the
sign)Example: Al+3
O-2
= Al2O3
If the valence is numerically equal, there is no need to criss -cross
since the sum of the valence is zero.Example: Ca+2
O-2
= CaO
Do not write the subscript if it is only 1.
If the subscript of the radical is greater than 1, the radical is enclosed
with a parenthesis. Example:Mg-2
PO-3
= Mg3 (PO2)2
Subscripts should be reduced to the lowest ratio.Example: Sn+4
O-2
=
Sn2 O4 = SnO2

8. How Are Compounds Named
These are compounds of weakly bonded H
atoms. In solution, they release ions. A given
nonmetal may form a series of acids.

9. Common Acids

10. Bases
identified by the presence of the hydroxide
group (OH). Name of the metallic portion first
followed by the word hydroxide.
Examples:
NaOH - Sodium Hydroxide
Fe(OH)2 - Iron(II) Hydroxide or Ferrous
Hydroxide
Fe(OH)3 - Iron(III) Hydroxide or Ferric
Hydroxide

11. Salts
Salts are formed when metallic atoms replace the weakly bonded
hydrogen atoms of an acid. They are named after the acid from
which they are formed. The name of the metal comes first, followed
by the name of the nonmetallic group. The ending ‘ic’ is changed to
‘ate’ and the ending ‘ous’ to ‘ite’. For salts with no oxygen atom, the
prefix ‘hydro’ is dropped and ending ‘ic’ is changed to ‘ide’.
For example, the acid HNO3 (nitric acid) forms the salt
KNO3 (potassium nitrate), when the metallic atom K places H atom
of the acid. As another example, the acid HNO2 (nitrous acid) forms
the salt KNO potassium nitrate). The ending ‘ous’ of the acid is
changed to ‘ite’.
HI (hydroiodic acid) forms the salt KI (potassium iodide). Since
there is no more hydrogen atom in the salt, the prefix “hydro” of the
acid name is dropped. The ending ‘ic’ of the acid is changed to “ide’
in salt.

12. Oxides
are compounds of oxygen with metals or nonmetals.
Name the metal or the nonmetal first. Then use the
prefixes di, tri, tetra or penta before the term oxide to
indicate the number of oxygen atoms present. In case
where the number of oxygen atom present can
determine from oxidation number of the combined
metal, the prefix is omitted.
Examples:
1.NO2: Nitrogen Dioxide
2.N2O4: Dinitrogen Tetroxide
3.P2O5: Phosphorus Pentoxide
4.PbO: Lead(II) oxide or Plumbous Oxide
5.PbO2: Lead(IV) oxide or Plumbous Oxide

13. Questions for Study and Review
I. Name the following compounds by identifying the oxidation number of the metal as
you name the compounds listed below:
1. KCl
2. PbS
3. CrSO4
4. Fe(NO3)2
5. Sn(ClO4)3
II. Formula Writing: Write the correct chemical formula of the following:
1. Calcium carbonate
2. Magnesium hydroxide
3. Copper sulfate
4. Carbon tetrachloride
5. Potassium bromate
6. Ammonium hydroxide
7. Lead nitrate
8. Sulfuric acid
9. Nitric acid
10.Boric acid