v Elements are
classified broadly into two categories on the basis of properties:
v Metals:
Iron, Zinc, Copper, Aluminium etc.
v Non- metals:
Chlorine, Nitrogen, Hydrogen, Oxygen, Sulphur etc.
v Apart from
metals and non-metals some elements show properties of both metals and non-metals,
Example:
Silicon, Arsenic, Germanium.They are called metalloids.
Comparison of physical and chemical
properties of metals and non – metals:-
|
Sl. No.
|
Property
|
Metals
|
Non-Metals
|
|
1
|
Physical
State
|
Metals are
solid at room temperature. Except mercury and gallium.
|
Non-metals
generally exist as solids and gases, except Bromine.
|
|
2
|
Melting
and boiling points
|
Metals
generally have high m.pt and b.pt except gallium and caesium.
|
Non-metals
have low m.pt and b.pt except diamond and graphite.
|
|
3
|
Density
|
Generally
high.
|
Generally
low.
|
|
4
|
Malleability
and Ductility
|
Malleable
and ductile.
|
Neither
malleable nor ductile.
|
|
5
|
Electrical
and thermal conductivity
|
Good
conductors of heat and electricity.
|
Generally
poor conductors of heat and electricity except graphite.
|
|
6
|
Luster
|
Poses
shining lustre.
|
Do not
have lustre except iodine.
|
|
7
|
Sonorous
sound
|
Give
sonorous sound when struck.
|
Does not
give sonorous sound.
|
|
8
|
Hardness
|
Generally
hard except Na, K
|
Solid
non-metals are generally soft except diamond.
|
Comparison of Chemical Properties of
Metals and Non-metals:-
|
1
|
Reaction
with Oxygen
|
Metal + Oxygen® Metal
oxide
4Na(s) + O2(g) ® 2Na2O(s)
4Al(s) + 3O2(g) ® 2Al2O3
Metals
form basic oxides. Zn and Al
form amphoteric oxides (they show the properties of both acidic and basic
oxides)
Most of the metal oxides are insoluble in water. Some of them dissolve
to form Alkali
Na2O(s) + H2O(l) ® 2NaOH(aq)
|
Non-metal + Oxygen ® Non-metal
oxide C
+ O2® CO2
S + O2® SO2
Non-metals
form acidic oxides.
CO and H2O are neutral oxides(they are neither acidic nor
basic in nature). Non-metal oxides are soluble in water
They dissolve in water to form acid. example SO2 +H2O
® H2SO3
|
|
2
|
Reaction
with water
|
Metals react with water to form
metal oxides or metal hydroxide and H2 gas is released. 2Na(s) + 2H2O(l)
® 2NaOH
+
H2(g)
+ heat
|
Non-metals
do not react with water, steam to evolve hydrogen gas. Because Non-metals
cannot give electrons to hydrogen in water so that it can be released as H2
gas.
|
|
3
|
Reaction
with dilute Acids
|
Metal + Acid ® Metal
salt + Hydrogen
Mg(s)+2HCl(aq)Ã MgCl2(aq)+H2(g)
2Na(s)+H2SO4Ã Na2SO4(aq)
+H2(g)Metal+HNO3Ã H2 gas is not
displaced. Reason- HNO3 is strong
oxidizing agent. It oxidises hydrogen to water.
|
Non-metals
do not react with acids to release H2 gas Reason- Non-metals cannot loose electrons and give it to Hydrogen
ions of acids so that the gas is released.
|
|
4
|
Reaction
with salt solutions
|
When
metals react with salt solution, more reactive metal will displace a less
reactive metal from its salt solution.
CuSO4(aq)+Zn(s)Ã ZnSO4(aq)+Cu(s)
|
When
non-metals react with salt solution, more reactive non-metal will displace a
less reactive non-metal from its salt solution.
2NaBr(aq)+Cl2(g)Ã 2NaCl(aq)+Br2(aq)
|
|
5
|
Reaction
with Chlorine
|
Metal +
Chlorine à Metal
Chloride
ionic bond is formed. Therefore Ionic compound is obtained. 2Na + Cl2Ã 2NaCl
|
Non-metal
+ Chlorine à Non-metal
Chloride.
Covalent
bond is formed. Therefore covalent compound is obtained. H2(g) + Cl2Ã 2HCl
|
|
6
|
Reaction
with Hydrogen
|
Metals
react with hydrogen to form metal hydride.
This
reaction takes place only for most reactive metals. 2Na(s) + H2(g)
à 2NaH(s)
|
Non-metals
react with hydrogen to form hydrides
H2(g)
+ S(l) Ã H2S(g)
|
Properties of ionic compounds
- Physical nature:solid and hard due to strong force of
attraction. (generally brittle)
- Melting point and boiling point:have high M.P and B.P, as large amount of heat
energy is required to break strong ionic attraction.
- Solubility: soluble in water and insoluble in kerosene and pertrol.
- Conduction of electricity:ionic compounds in solid state-----does not
conduct electricity.
Reason—Ions can not move due to rigid solid structure. Ionic
compounds conduct electricity in molten state.
Reason-- Ions can move freely since the electrostatic forces of
attraction between the oppositely charged ions are overcome due to heat.
Occurrence of metals.
It occurs in
Earths crust, sea-water
|
Ores
|
|
Minerals
|
Elements or compounds, occuring naturally Minerals that
contain very high percentage
in the earth’s crust of
a perticular metal and these metals can be
extracted economically on a large scale.
e.g
Bouxite ore → Aluminium
Haematite → Iron
EmoticonEmoticon