Elements are classified broadly into two categories on the basis of properties: Metals: Iron, Zinc, Copper, Aluminium etc.
Non – metals: Chlorine, Nitrogen, Hydrogen, Oxygen, Sulphur etc.Apart from metals and non-metals some elements show properties of both metals and non – metals, e.g. Silicon, Arsenic, Germanium .They are called metalloids
Comparison of physical and chemical properties of metals and non – metals:-
|
S.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 cesium. |
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 luster. | Do not have luster 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 HO2O are neutral oxides(they are neither acidic nor basic in nature) Non- metal oxides are soluble in water They dissolve in water to form acids 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
HCl |
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. Mn + 2HNO3→ Mn(NO3)2 + H2 H2 gas from HNO3 |
|
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) + n(s)→ 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)→ 2NaCl(aq) + Br2(aq) |
|
5 |
Reaction with Chlorine | Metal + Chlorine→ Metal Chloride ionic bond is formed. Therefore Ionic compound is obtained. 2Na+ Cl2 → 2NaCl |
Non-metal + Chlorine→Non-metal Chloride
covalent bond is formed. Therefore covalent compound is obtained. H2(g) + Cl2 → 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) → 2NaH(s) |
Non-metals react with hydrogen to form hydrides H2(g) + S(l) → H2S(g) |
| Properties of ionic compounds | ||||
| 1. | Physical nature | : | solid and hard due to strong force of attraction. (generally brittle) | |
| 2. | 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. | |
| 3. | Solubility | : | soluble in water and insoluble in kerosene and pertrol. | |
| 4. | 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. | ||||
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Occurrence of metals. It occurs in Earths crust, sea-water
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Minerals Elements or compounds, occuring naturally in the earth‘s crust |
Ores Minerals that contain very high percentage of a perticular metal and these met als can be extracted economically on a large scale. |
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