FIRST TWENTY ELEMENTS AND THEIR ATOMIC NUMBER, SYMBOL AND
VALENCY
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ATOMIC
NUMBER(Z)
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NAME OF
ELEMENT
|
SYMBOL
|
VALENCE
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1
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Hydrogen
|
H
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(-1), +1
|
2
|
Helium
|
He
|
0
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3
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Lithium
|
Li
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+1
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4
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Beryllium
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Be
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+2
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5
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Boron
|
B
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-3, +3
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6
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Carbon
|
C
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(+2), +4
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7
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Nitrogen
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N
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-3, -2,
-1, (+1), +2, +3, +4, +5
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8
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Oxygen
|
O
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-2
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9
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Fluorine
|
F
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-1, (+1)
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10
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Neon
|
Ne
|
0
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11
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Sodium
|
Na
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+1
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12
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Magnesium
|
Mg
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+2
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13
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Aluminum
|
Al
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+3
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14
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Silicon
|
Si
|
-4,
(+2), +4
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15
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Phosphorus
|
P
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-3, +1,
+3, +5
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16
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Sulfur
|
S
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-2, +2,
+4, +6
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17
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Chlorine
|
Cl
|
-1, +1,
(+2), +3, (+4), +5, +7
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18
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Argon
|
Ar
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0
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19
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Potassium
|
K
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+1
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20
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Calcium
|
Ca
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+2
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CHEMICAL COMPOUND FORMULAS
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S.No
|
NAME OF
THE CHEMICAL COMPOUND
|
FORMULA
|
1
|
Acetic
acid(Vinegar)
|
CH3COOH
|
2
|
Hydrochloric
acid
|
HCl
|
3
|
Sulfuric
acid
|
H2SO4
|
4
|
Oxygen
gas
|
O2
|
5
|
Sodium bicarbonate(Baking
soda)
|
NaHCO3
|
6
|
Sodium chloride(Common salt)
|
NaCl
|
7
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Ammonium hydroxide
|
NH4OH
|
8
|
Sodium hydroxide
|
NaOH
|
9
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Magnesium hydroxide(milk of magnesia)
|
Mg(OH)2
|
10
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Copper sulphate
|
CuSO4
|
11
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Iron(II) sulphate
|
FeSO4
|
12
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Magnesium oxide
|
MgO
|
13
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Calcium carbonate
|
CaCO3
|
14
|
Iron oxide(rusted iron)
|
Fe2O3
|
15
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Carbondioxide
|
CO2
|
16
|
Sodium bromide
|
NaBr
|
17
|
Zinc sulphide
|
ZnS
|
18
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Sulphur dioxide
|
SO2
|
19
|
Zinc chloride
|
ZnCl2
|
20
|
Lead(II) nitrate
|
Pb(NO 3 )2
|
21
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Aluminum chloride
|
AlCl3
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22
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Nitric acid
|
HNO3
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23
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Sulphuric acid
|
H2SO4
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24
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Carbonic acid
|
H2CO3
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25
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Water
|
H2O
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SOME OF BASIC RADICALS AND THEIR
POSITIVE VALENCE
Plus One Valence
|
Plus Two Valence
|
Plus Three Valence
|
Plus Four Valence
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Ammonium
|
NH4+
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Calcium
|
Ca2+
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Aluminum
|
Al3+
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Lead(Plumbic)
|
Pb4+
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Cuprous/Copper(I)
|
Cu+
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Zinc
|
Zn2+
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Ferric/Iron(III)
|
Fe3+
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Potassium
|
K+
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Cupric/Copper(II)
|
Cu2+
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Carbon
|
C4+
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Silver
|
Ag+
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Ferrous/Iron(II)
|
Fe2+
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Antimony
|
Sb3+
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Silicon
|
Si4+
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Sodium
|
Na+
|
Lead(II)/Plumbous
|
Pb2+
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Arsenic
|
As3+
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Magnesium
|
Mg2+
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Chromium
|
Cr3+
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Manganese
|
Mn2+
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SOME ACIDIC RADICALS AND THEIR VALENCY
Minus One Valence
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Minus Two Valence
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Minus Three Valence
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Minus Four Valence
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Acetate(C2
H3O 2)
|
CH3COO-
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Carbonate
|
CO32-
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Phosphate
|
PO43-
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Silicate
|
SiO4
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Bicarbonate
|
HCO3-
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Oxide
|
O2-
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Ferrocyanide
|
Fe(CN) 6
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Bromide
|
Br-
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Sulfide/Sulphide
|
S2-
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Chloride
|
Cl-
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Sulfite
/Sulphite
|
SO32-
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Fluoride
|
F-
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Sulfate
|
SO42-
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Hydroxide
|
OH-
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Iodide
|
I-
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Nitrate
|
NO3-
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Permanganate
|
MnO4-
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BOHR’S MODEL OF ATOM
How
are Electrons Distributed in Different Orbits (Shells)?
(i) The maximum number of electrons present in a shell
is given by the formula 2n2, where ‘n’ is the orbit number or energy
level index, 1,2,3,….
Hence the maximum number of electrons in different
shells are asfollows:
first orbit or
K-shell will be = 2 X 12 = 2,
second orbit or
L-shell will be = 2 X 22= 8,
third orbit or
M-shell will be = 2 X 32 = 18,
fourth orbit or N-shell will be = 2 X 42=
32, and so on.
(ii)
The maximum number of electrons that can be accommodated in the outermost orbit
is 8.
(ii) Electrons are not accommodated in a given shell,
unless the inner shells are filled. That is, the shells are filled in a step-wise
manner.
SUBATOMIC PARTICLE
|
SYMBOL/REPRESENTATION
|
Electron
|
e−,
β−
|
Proton
|
p+,
p, N+
|
Neutron
|
n, n0,
N0
|
ATOMIC STRUCTURE OF THE FIRST
EIGHTEEN ELEMENTS IS SHOWN SCHEMATICALLY
Writing of chemical formula for a compound
