Language of Chemistry

1. THE LANGUAGE OF
CHEMISTRY
- Valency andvariable valency

2. N JNKN,N KNKNKNKNKN KJNIJHNMKNJKNKNJKNJKKNJKNJK
VALENCY
Definition: The combiningcapacity of an element or of
a radicalto form molecules is knownas valency.
Valencycanbe even zero
(e.g. inert gases)

3. S.No. Name of the element Symbol Valency
1. Hydrogen H 1
2. Helium He 0
3. Carbon C 4
4. Nitrogen N 3
5. Oxygen O 2
6. Fluorine F 1
7. Neon Ne 0
8. Sodium Na 1
9. Magnesium Mg 2
10. Aluminium Al 3
11. Argon Ar 0
VALENCIESOFSOME ELEMENTS

4. VALENCIESOFSOME RADICALS
NAME OF THE RADICAL SYMBOL VALENCY
Sodium Na+
1
Potassium K+
1
Ammonium NH4
+
1
Magnesium Mg2+
2
Calcium Ca2+
2
Zinc Zn2+
2
Aluminium Al3+
3
Hydroxide OH-
1
Chloride Cl-
1
Carbonate CO3
2-
2
Sulphate SO4
2-
2
Nitride N3-
3
Phosphate PO4
3-
3

5. N JNKN,N KNKNKNKNKN KJNIJHNMKNJKNKNJKNJKKNJKNJK
VARIABLE VALENCY
Definition: Elementsshowing more than one valency is
known as variable valency.
E.g. Iron exhibitthe valencies2 and 3
Copper exhibitthe valencies 1 and 2

6. N JNKN,N KNKNKNKNKN KJNIJHNMKNJKNKNJKNJKKNJKNJK
HOW TO DENOTE VARIABLE VALENCY?
For lowervalency,the suffix‘ous’ should be added to
the name of the element
E.g. Iron is named as ‘Ferrous’ when it exhibits the
valency2. (lower valency)

7. N JNKN,N KNKNKNKNKN KJNIJHNMKNJKNKNJKNJKKNJKNJK
HOW TO DENOTE VARIABLE VALENCY?
For highervalency,the suffix‘ic’ should be added to the
name of the element
Eg: Iron is named as ‘Ferric’when it exhibits thevalency
3. (highervalency)

8. N JNKN,N KNKNKNKNKN KJNIJHNMKNJKNKNJKNJKKNJKNJK
HOW TO DENOTE VARIABLE VALENCY?
Instead of using suffixes,roman numeralscanalso be
used.
The valencyis represented in roman numeralsenclosed
in brackets
Eg: ‘Ferrous’ is represented as Iron(II)and‘Ferric’as
Iron(III)

9. VALENCIESOFSOME RADICALS
NAME OF THE
ELEMENT
SYMBOL LOWER VALENCY STATE HIGHER VALENCY STATE
Copper Cu Cu+ or Cu(I)
Copper(I) / Cuprous
Cu2+ or Cu(II)
Copper(II)/ Cupric
Silver Ag Ag+ or Ag(I)
Silver(I)/ Argentous
Ag2+ or Ag(II)
Silver(II)/ Argentic
Iron Fe Fe2+ or Fe(II)
Iron(II)/Ferrous
Fe3+ or Fe(III)
Iron(III)/Ferric
Lead Pb Pb2+ or Pb(II)
Lead(II)/ Plumbous
Pb4+ or Pb(IV)
Lead(IV)/ Plumbic

10. Significance of molecular
formulae
 Chemical equations
UPCOMING TOPICS …