Metals and Non-Metals | Chemistry Revision Notes
Metals and Non-Metals: At present, there are about 118 elements known on this earth. On the basis of their properties, elements can be classified as metals and non-metals. Also, there are some elements that have both the property of metals and non-metals. Such elements are called metalloids.
Metals and Non-Metals
The elements that lose electrons and form positive ions are called metals. Example: copper, iron, sodium, etc.
And those elements that gain electrons and form a negative ion are called non-metals. Example: oxygen, chlorine, nitrogen, etc. Non-Metals are generally present in solids and gases form except bromine which is present in liquid form.
Physical Properties Of Metals
- Metals generally have a shiny surface. This property is called metallic lustre. Example: gold, silver, platinum
- They are generally very hard and their hardness varies from metal to metal. Alkali metals like sodium and potassium are very soft that they can be cut with a knife.
- Metals have a property of ductility that is they can be made into thin wire. Gold is the most ductile metal
- Metals have a property of malleability that is they can be beaten into thin sheets. Gold and silver are the most malleable
- Metals are generally good conductors of heat and electricity. Silver and copper are good conductors of heat whereas lead and mercury are poor conductors.
- Metals have a property of sonority. They make sounds on beating each other
- Metals generally have high melting and boiling point. Metals like gallium and cesium have a low melting point that they can melt on our palm whereas tungsten has a high melting point
Physical Properties Of Non-Metals
- Non-Metals don’t have a shiny surface. But some non-metals like a diamond, graphite, iodine have a shiny surface.
- They are brittle in nature. They broke into pieces when hammered
- Non-metals don’t have the property of malleability and ductility.
- Many non-metals are soft but diamond which is a non-metal is one of the hardest substances on this earth.
- They are generally poor conductors of electricity and heat. But graphite which is non-metal is a good conductor of electricity.
- Non-metals have low melting and boiling point.
Chemical Properties Of Metals
Reaction with oxygen
Metals reacts with oxygen to form metal oxide.
Metal + oxygen = metal oxide
Example: Sodium reacts with oxygen to form sodium oxide
Na + O2 = Na2O
- Some metal oxides like aluminum and zinc oxide show both the acidic and basic character and reacts with both acids and bases to form salt and water are called amphoteric oxides.
Example: Aluminium reacts with both acids and bases
Al2O3 + 6HCl = 2AlCl3 + 3H2O
Al2O3 + 2NaOH = 2NaAlO2 + H2O
The metal oxides which are soluble in water are called alkalis.
- Different element reacts with oxygen at different rate. Sodium and potassium are very reactive element. They catches fire when they come in contact with air. To prevent this they are stored in kerosene.
- Magnesium and aluminium reacts with oxygen and a layer of oxide is formed which prevent from further oxidation.
- Zinc reacts only on strong heating and copper doesn’t does not reacts with oxygen even on heating
- Silver and gold are least reactive metals , they react with oxygen.
- The process of forming thinks aluminium oxide layer is called anodizing. the thin aluminium oxide layer can be made thicker by this process in which the electrolysis process is used.
Reaction with water
Metals react with water to form metal oxides and hydrogen gas. Metal oxides further reacts with water to form metal hydroxide.
Metal + water = Metal oxide + Hydrogen gas
Metal oxide + water = Metal hydroxide
- Some metals like sodium and potassium react vigorously with cold water and heat is released.
K + 2H2O = KOH + H2 + Heat
Na + 2H2O = NaOH + H2 + Heat
The heat produced in above cases burns the hydrogen gas.
- Calcium and magnesium reacts with cold water less vigorously.
Ca + H2O = Ca(OH)2 + H2
The released in the above reaction is not sufficient to burn and hydrogen gas. The hydrogen bubbles makes the calcium metal to float.
- Some metals like iron don’t react with hot and cold water but they react with steam to form a metal oxide and hydrogen gas
3Fe + 4H2O = Fe3O4 + 4H20
- Silver, gold, copper, and lead don’t react with water.
Reaction With Acids
Metals reacts with acids to form salt and hydrogen gas.
Metal + Acid = Salt + hydrogen gas
Example: Zn + HCl = ZnCl2 + H2
Exception : If a metal reacts with nitric acid (HNO3), hydrogen gas is not released. This is because nitric acid is a strong oxidizing agent. It oxidizes the hydrogen gas released and it self get reduced to N2O , NO , NO2.
But if Mn and Mg reacts with nitric acid , hydrogen gas is released.
Aqua regia is a mixture of concentrated hydrochloric acid and nitric acid in the ratio of 3:1. It can dissolve gold which no other liquids or acids can do.
Reaction With Metal Salts
More reactive metal displaces the less reactive metal from its salt solution. This type of reaction is called displacement reaction.
Example:CuSO4 + Fe = FeSO4 + Cu
Chemical properties of Non-Metals
Non-metals don’t react with water at any state and with dilute acids
This is because non-metals accept the electron, they cant give electrons to H+ ions of acids to reduce them to hydrogen gas. But they react with acids on heating
Also like metals , non-metals also show displacement reaction.
Example: Cl2 + 2NaBr = 2NaCl + Br2
Reactivity series of metals
A series of metals which are arranged in the decreasing order of their reactivity.
Ionic bond between metals and non-metals.
Metals lose electron and form a positive ion called cation and non-metals gain electrons to form a negative ion called anion. Metals and non-metals react to achieve octet.
A type of chemical bonding where electrons are transferred from one atom to another atom is called an ionic bond.
Ex: Electronic configuration of magnesium is K L M. If it loses 2
2 8 2
electrons from its last shell it becomes octet.
Electronic configuration of oxygen is K L , it requires 2 electrons to
Complete its octet. So magnesium and oxygen reacts together to form a ionic bond.
Properties of Ionic Compounds
- Ionic compounds are solid as there is a strong electrostatic force of attraction between positive and negative ions. But break into pieces when hammered
- Because of strong electrostatic force of attraction between ions , larger heat energy is required to over this force. So they have a higher melting and boiling point
- These compounds are soluble in water but insoluble in organic solvents like kerosene, benzene etc.
- Ionic compounds in molten and aqueous state conduct electricity because of free ions. But in solid state , there are no free ions and hence it doesn’t conduct electricity in solid state.
Occurrence of Metals
- The elements or compounds that are present in the earth crust are called minerals and metals which are extracted from minerals are called ores.
- Metals at the top of the reactivity series are very reactive and are present in the nature as free elements.
- The metals in the middle of the reactivity series are found in the form of oxides , sulphides , carbonates.
- Metals at the bottom of the reactivity series are less reactive so they are present in free state. Ex: gold , silver etc.
- So the extraction method used depend on the position of the element in the reactivity series.
- The following flow chart explains the method used:
There are some impurities in the ores which are called as gangue and removal these gangue is called concentration of ore.
Extraction of metal of low reactivity:
These metals are less reactive . so they can obtained by heating their oxides.
- Cinnabar: the ore of mercury HgS is obtained by heating it in presence of oxygen and then mercuric oxide is then heated to obtain mercury.
2HgS + 3O2 = 2HgO + 2SO2
2HgO + Heat = 2Hg + O2
- Similarly Cu2S Is heated to get Cu
2Cu2S + 3O2 = 2Cu2O + 2SO2
2Cu2O + Cu2S + Heat = 6Cu + SO2
Extraction of metal in middle of reactivity series
These metals like iron , copper are present in nature in sulphide and carbonate form which are converted into oxides and then reduced to obtain the metal.
Roasting: In the process, the sulfide ore is heated in presence of oxygen to convert into metal oxides.
Example: 2ZnS + 3O2 = 2ZnO + 2SO2
- Calcination: In this process carbonate ores are heated in the absence of oxygen to convert it into metal oxides.
Example: ZnCO3 + Heat = ZnO + CO2
- Reduction: Finally metal oxides are reduced into metal. It is done by heating the metal oxide with a reducing agent.
ZnO + C = Zn + CO
Sometimes displace reactions are used to obtain these metals. These displacement reactions are highly exothermic.
Example: Iron oxide is reacted with aluminiun , which is used to join railway tracks. This process is called a thermite reaction.
Fe2O3 + Al = 2Fe + Al2O3
Extraction of highly reactive metals
These metals are obtained by the process of electrolytic reduction.
- In electrolytic reduction salts of metals are taken and electricity is passed through it
- Ex: molten NaCl is electrolysed and sodium is obtained at cathode and chlorine is obtained at anode.
Refining of metals
The metals obtained after the reduction process still have some impurities and these are removed by the process called electrolytic refining.
- A thick block of impure metal is made anode
- A thin strip of pure metal is made cathode
- A salt of metal is taken as an electrolyte
- On passing current, pure metal from anode gets into electrolyte and same amount of metal gets deposited on cathode.
- The soluble impurities gets dissolved in the solution and insoluble impurities settle at the bottom of the anode called as anode mud.
- The following is an activity gives an example of purification of copper metal.
The process by which metals are attached by air and water is called corrosion. Ex: iron gets covered by reddish brown colour.
Prevention of corrosion
- It can be prevented by painting
- It can be prevented by greasing or oiling
- It can be prevented by galvanization. In this process a layer of zinc is applied on the metal.
- It can also prevented by tin plating, copper plating.
- An alloy is an homogenous mixture of two or more metals or non-metal.
- An alloy has less melting point and electrical conductivity.
- Brass (alloy of copper and zinc) and bronze (alloy of copper and tin) are poor conductors of electricity.
- Solder an alloy of lead and tin has a low melting point
- Alloy of mercury is called as amalgam.
- Pure gold is 24 carate. It is mixed with copper or silver to increase its strength.
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