Chemical Properties Of Non - Metals
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Chemical Properties Of Non - Metals
Metal And Non-metals of Class 10
CHEMICAL PROPERTIES OF NON - METALS
Non-metals are less reactive than metals. They react with oxygen and salts solutions, but they do not react with water or dilute acids. In the ensuing discussions we will study these reactions. These reactions will give us some idea about chemical reactivity of non-metals.
Non-metals are electronegative :
Atoms of non-metal elements have 1 to 4 electrons less in the outermost shells. The atoms can therefore accept electrons while forming compounds. The non-metal atoms therefore become electronegative in a reaction. For example, Cl atom easily takes one electron in the M-shell to become Cl–.
Reaction with oxygen :
Non-metals react with oxygen to form non-metal oxides. Non-metal oxides are acidic or neutral in nature. Carbon forms carbon dioxide , which is an acidic oxide. Sulphur forms sulphur dioxide .This is also acidic in nature. Hydrogen form di-hydrogen oxide (water), which is neutral in nature. Acidic oxides dissolve in water to produce acids. Non-metal oxide bonds are covalent bonds. Non-metal atoms share electrons with oxygen atoms while forming the non-metal oxide. All non-metals have to be burnt is air or oxygen to form the subsequent non-metal oxides.
(a) S + O 2 → SO 2
Sulphur dioxide
Sulphur dioxide when dissolved in water forms sulphurous acid.
SO 2 + H 2 O → H 2 SO 3
Sulphurdioxide Sulphurousacid
(b) Similarly, carbon forms carbon dioxide and phosphorus forms phosphorus pentoxide. These oxides also give acidic solutions when dissolved in water.
C + O 2 → CO 2
Carbondioxide
CO 2 + H 2 O → H 2 CO 3
Carbonic acid
(c) P 4 + 5O 2 → 2P 2 O 5
Phosphorus pentoxide
P2O5 + 3H 2 O → 2H 3 PO 4
Phosphoric acid
Non-Metal reaction with water :
All non-metals do not react with water to form either metal oxides or metal hydroxides. Whether the water is in the form of cold water, hot water or steam, all non-metals remain unresponsive to water. The reason for this is the typical electronic configuration of non-metals. Non-metals are electronegative are unable to break the bond between H and O in water. The non-metals cannot reduce hydrogen by donating electrons.
Non-Metal reaction with dilute acids :
Most non-metals do not react with dilute acids. They are not capable of replacing hydrogen from the acids and forming a salt. For example C, S or P do not react with HCl or H2SO4 to give off hydrogen. The reason for this as discussed above. To release H+ from the acid, the non-metal has to provide the extra electron. Non-metals themselves are acceptors of electrons. Hence they are unable to displace H+ from the acid to form a salt and release hydrogen gas. Thus when non-metals like C, S, P are added to a test tube containing dilute acids, there will be no reaction or evolution of hydrogen gas.
Non-Metal reactions with salt solutions :
Reactivity of non-metals determine which salt is formed when a non-metal is added to a salt solution. More reactive non-metal displaces the less reactive non-metal in the metal salt. Example below will show a typical example.
This is a displacements reaction. A more reactive non-metal like chlorine (Cl) is displacing a less reactive non-metal bromine (Br) to form sodium chloride from sodium bromide.
When chlorine is passed through a solution of sodium bromide, then sodium chloride and bomine are formed.
2NaBr + Cl 2 → 2NaCl + B r2
Sodium Bromide Chlorine Sodium Chloride Bromine
Non-Metal reactions with chloride :
Non-metals react with chlorine (Cl) to form chlorides. These are covalent compounds and are non electrolytes when in solution. Some of the reactions are shown below.
(a) Hydrogen reacts with chlorine to form covalent chloride called hydrogen chloride.
H 2 + Cl 2 → 2HCl
Hydrogen chloride
(b) Phosphorus reacts with chlorine to form covalent chloride called phosphorus trichloride and phosphorus pentachloride.
P 4 + 6Cl 2 → 4PCl 3
Phosphorus trichloride
P4 + 10Cl 2 → 4PCl 5
Phosphorus pentachloride
Non-Metal reactions with hydrogen:
Non-metals react with hydrogen to form hydrides. These are covalent compounds unlike the metal-hydrides. The reactions are shown below.
(a) 2H 2 + O 2 → 2H 2 O
Water
(b) N 2 + 3H 2 → 2NH 3
Ammonia
(c) H 2 + S → H 2 S
Hydrogen sulphide
Oxygen combines with hydrogen to give a neutral non-metal hydride called water!! Similarly other common non-metal hydrides are methane (CH4) and hydrochloric acid (HCl). Non-metal hydrides are generally liquids or gases and because of their covalent nature, they do not conduct electricity.
Non-Metals as oxidizing agents :
Other than carbon, all non-metals accept electrons. Therefore they are oxidizing agents, they extract electrons from the neighboring elements. Chlorine is an oxidizing agent because it accepts an electron in its outermost orbit. It is interesting to note that even though chlorine is an oxidizing agent, it itself is getting reduced into becoming a chlorine ion.
Carbon is sometimes a reducing agent when it gives up its electrons in a reaction. For example in the formation of radicals, carbon donates electrons.
(a) Zn + S → Zn 2+ S 2–
Zinc sulphide
(b) 2Na + Cl 2 → 2Na + Cl –
Sodium chloride
DIFFERENCE BETWEEN METALS AND NON-METALS (CHEMICAL PROPERTIES)
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1. Action with mineral acids |
Metals generally react with dilute mineral acids to liberate hydrogen gas. |
Non-metals do not displace hydrogen on reaction with dilute minerals acids. |
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2. Nature of oxides |
They form basic oxides. For example, Na 2 O, MgO, etc. These oxides are ionic in nature. |
Non-metals form acidic or neutral oxides. For example, SO 2 , CO 2 , P 2 O 5 , are acidic whereas CO, N 2 O, are neutral. These oxides are covalent in nature. |
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3. Combination with hydrogen |
Metals generally do not combine with hydrogen. However Li, Na, Ca, etc. form unstable hydrides. For example, LiH, NaH, CaH 2 etc. These hydrides are ionic in character. |
Non-metals combine with hydrogen to form stable hydrides. For example, HCl, H 2 S, CH 4 , NH 3 , PH 3 , etc. These hydrides are covalent. |
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4. Combination with halogens |
They combine with halogens to form well defined and stable crystalline solids. For example, NaCl, KBr, etc. |
Non-metals form halides which are unstable and undergo hydrolysis readily. For example, PCl 5 , PCl 3 , etc. |
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5. Electrochemical behaviour |
Metals are electropositive in character. They form cations in solution and are deposited on the cathode when electricity is passed through their solution. |
Non-metals are electronegative in character. They form anions in solution and are liberated at the anode when their salt solutions are subjected to electrolysis. Hydrogen in an exception. It usually forms positive ions and is liberated at cathode. |
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6. Oxidising or reducing behaviour |
Metals behave as reducing agents. This is because of their tendency to lose electrons. Na ⎯→ Na + + e – |
Non-metals generally behave as oxidising agents since they have the tendency to gain electrons. ½Cl 2 + e - → Cl - |
Uses of metals
Metals are absolutely indispensable to all living beings. Some of the uses of metals are
- Metals are present in minute quantities in all living organisms. Na and K are major metals that that are used for transmission of electrical signals from the brain to the entire nervous system.
- Iron is an important component of hemoglobin in the blood of warm-blooded animals. Iron transports oxygen to issues by forming oxides. In cold-blooded animals, blood contains copper.
- Chlorophyll in plants contains magnesium. Other metals like copper, zinc etc. are needed by different tissues in a human body for functioning properly.
- In addition to the use of metals for living organisms, metals are used extensively by humans. Applications of metals for useful purposes can be categorized as follows:
- Iron is used as a catalyst in the preparation of ammonia gas by Haber’s process.
- Zinc is used for galvanizing iron to protect it from rusting.
- Chromium and nickel metals are used for electroplating and in the manufacture of stainless steel.
- The aluminium foils are used in packaging of medicines, cigarettes and food materials.
Aluminium Foil
- Silver and gold metals are used to make jewellery. The thin foils made of silver and gold are used to decorate sweets.
- The liquid metal ‘mercury’ is used in thermometers.
- Ti finds extensive use in aircraft industries.
- Al finds extensive use in space and auto industries.
- Pure metals, which display zero resistance to electrical currents, are called superconductors. Hg, Nb are examples of superconductors. They become superconductors below a critical temperature of 4.2 and 9.2 K respectively. Superconductors have many applications in research and industry.The list is endless but the above list gives you a brief idea about the use of pure metals.
USES OF NON-METALS
The important uses of non-metals are as follows:
- Hydrogen is used in the hydrogenation of vegetable oils to make vegetable ghee (or vanaspati ghee).
- Hydrogen is used in the manufacture of ammonia (whose compounds are used as fertilisers).
- Liquid hydrogen is used as a rocket fuel.
- Carbon (in the form of graphite) is used for making the electrodes of electrolytic cells and dry cells.
- Nitrogen is used in the manufacture of ammonia, nitric acid and fertilisers.
- Due to its inertness, nitrogen is used to preserve food materials.
- Compounds of nitrogen like Tri Nitro Toluene (TNT) and nitroglycerine are used as explosives.
- Sulphur is used for manufacturing sulphuric acid.
- Sulphur is used as a fungicide and in making gun powder.
- Sulphur is used to the vulcanisation of rubber.
