Table 1: Symbols of Elements
First 20
Elements and their Symbols
Name
|
Symbol
|
Name
|
Symbol
|
Hydrogen
|
H
|
Sodium
|
Na
|
Helium
|
He
|
Magnesium
|
Mg
|
Lithium
|
Li
|
Aluminium
|
Al
|
Beryllium
|
Be
|
Silicon
|
Si
|
Boron
|
B
|
Phosphorus
|
P
|
Carbon
|
C
|
Sulphur
|
S
|
Nitrogen
|
N
|
Chlorine
|
Cl
|
Oxygen
|
O
|
Argon
|
Ar
|
Fluorine
|
F
|
Potassium
|
K
|
Neon
|
Ne
|
Calcium
|
Ca
|
Valency:
Valency is
defined as the number of electrons an atom of an element can gain or lose to
form Ions.
For example:
Consider
Sodium with Atomic number; Z = 11
Electronic configuration of Sodium = 2, 8, 1
Valence
Electron = 1
The atom of
sodium can easily lose its valence electron to form sodium ion.
Number of
protons in the sodium ion = 11
Charge on
the nucleus in the sodium ion = +11
Number of
electrons in the sodium ion = 10
Number of
electrons in the sodium ion = -10
Net charge
on the sodium ion = +1
Therefore;
Sodium ion is written as Na+.
The + sign
shows:
- the number of protons are greater than the number of electrons
- electron(s) is(are) lost
- the coefficient of the plus sign shows the number of electron(s) lost
Note: All
metals and Hydrogen form CATIONS by LOSING ELECTRONS to form compounds.
Also;
consider Chlorine with Atomic number; Z = 17
Electronic configuration of Sodium = 2, 8, 7
Valence
Electron = 7
The atom of
chlorine can easily gain an electron to complete its valence shell to form
chloride ion.
Number of
protons in the chloride ion = 17
Charge on
the nucleus in the chloride ion = +17
Number of
electrons in the chloride ion = 18
Number of
electrons in the chloride ion = -18
Net charge
on the chloride ion = -1
Therefore;
chloride ion is written as Cl-.
The - sign
shows:
- the number of protons are less than the number of electrons
- electron(s) is(are) gained
- the coefficient of the minus sign shows the number of electron(s) gained
Note: All
non-metals and non-metallic radicals form ANIONS by GAINING ELECTRONS to form
compounds.
Table 2: Cations and Anions
Positively
Charged Ions
|
Negatively
Charged Ions
|
||
Sodium
|
Na+
|
Chloride
|
Cl-
|
Potassium
|
K+
|
Bromide
|
Br-
|
Silver
|
Ag+
|
Iodide
|
I-
|
Copper (I)
|
Cu+
|
Hydroxide
|
OH-
|
Hydrogen
|
H+
|
Nitrate
|
NO3-
|
Ammonium
|
NH4+
|
Hydrogen Carbonate
|
HCO3-
|
Lead
|
Pb+2
|
Hydrogen Sulphate
|
HSO4-
|
Copper (II)
|
Cu+2
|
Sulphate
|
SO4-2
|
Magnesium
|
Mg+2
|
Sulphite
|
SO3-2
|
Calcium
|
Ca+2
|
Carbonate
|
CO3-2
|
Zinc
|
Zn+2
|
Oxide
|
O-2
|
Barium
|
Ba+2
|
Sulphide
|
S-2
|
Iron (II)
|
Fe+2
|
Phosphate
|
PO4-3
|
Mercury
|
Hg+2
|
||
Iron (III)
|
Fe+3
|
||
Aluminium
|
Al+3
|
||
