We are presenting CBSE NOTES FOR QUICK REVISION

, Which help you to focus your attention and avoid distractions. As you read notes, you will be engaging your mind in identifying and organizing the main ideas of topic in minimum time span and make it easy to memorize the topic for best result.

We have also added CBSE MCQ Questions with answer in MCQ quiz format for your self assessment.

Elements can be divided in three groups depending on their physical and chemical properties:

  • Metals
  • Non-Metals
  • Metalloid

Metals

  • Elements which are hard, shiny can be beaten into sheets, drawn into wires and are good conductors of heat and electricity are generally metals. For example: copper, gold ,iron etc.
  • Metals like  Aluminum, magnesium, sodium, lead ,iron, copper, zinc and any other metal that is easily available.
  • Metals, in their pure form, have a shining surface. This property is called metallic luster.
  • The ability of metals of transforming into thin wires is called ductility. Gold is the most ductile metal.
  • The ability of metals of transforming into thin sheets when beaten is called malleability.
  • The ability to transform of metals into thin wires is called ductility.
  • Metals are good conductors of heat and have high melting points. Silver & copper are the best conductors of heat  & Lead and mercury are generally poor conductors of heat.
  • Metals are sonorous. They produce sound when struck. With the exceptions of sodium, potassium and mercury.
  • Generally metals have high melting and boiling point.
  • Metals have high densities.
  • Most metals have high tensile strength.
  • Metals at room temperature  are solids, except mercury, which is liquid at room temperature
  • Metals are generally hard and strong but sodium and potassium are soft solids and can be cut with a knife.
  • They are good conductors of heat and electricity. Silver is the best conductor of electricity followed by copper and gold, aluminum, and zinc.
  • Metals like gold, silver and copper have a luster and they shine and reflect light. Therefore they are lustrous.
  • Metals like gold, silver and copper have a luster and they shine and reflect light. Therefore they are lustrous.
  • The property of metals by virtue of which metal can be beaten into sheets is called malleability. We use aluminum foil to pack food.

Physical Properties Of Nonmetals:

  • Non-metals are not malleable so cannot be hammered into thin sheets.
  • Generally Non-metals are brittle as they break down into pieces on hammering.
  • Non-metals are not ductile so they cannot be drawn into wires.
  • Nonmetals are a poor conductor of heat and electricity. Except graphite which is allotropy, carbon conducts electricity.
  • Non-metals are not shiny (lustrous).
  • Non-metals have low tensile strength. Which means they can't hold heavyweights.
  • Non-metals are not sonorous.
  • Non-metals are soft.
  • The elements which have the properties of metals and non-metals are called metalloids. Such as boron, silicon, germanium, tellurium etc

    • What happens when Metals are burnt in Air?

     

     

    • When a metal reacts with oxygen and form a metal oxide. Which is basic in nature.

     

                 Metal + oxygen → metal oxide

     

    •  Copper when heated in air, it reacts with oxygen to form copper (II) oxide & a black oxide.

                                                   2Cu + O2 → 2CuO

     

    • When aluminum heated in air, it forms aluminum oxide.

     

                                                    4Al + 3O2 → 2Al2O3

    •  Calcium reacts with oxygen and form calcium oxide

     

                                        2Ca + O2→2CaO

     

    • Magnesium burns readily in air with a white light.

      

                                       2Mg + O2 → 2MgO

     

    Rate of reaction for metals with oxygen are not same. Different metals show different reactivates towards oxygen. Metals like potassium and sodium react so vigorously & they catch fire when they kept in the open.

     

    • Potassium gives lilac flame when heated in air.

                                      4K+ O2 ➞ 2K2O

    ·                              Sodium  reacts vigorously with oxygen and water. 

                                     4 Na + O2 → 2 Na2O

     

           Sodium (metal)is a very reactive . It react with oxygen to form sodium oxide but this is an unstable compound and soon reacts with hydrogen to form sodium hydroxide. 

                                  Na2O+H2O→2NaOH

     

    • Rusting is an oxidation reaction. The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we call rust. Its appearance is reddish-brown.

    Rust is a Hydrated Iron (III) Oxide whose chemical formula is Fe2O3• 32H2O. 

     

                                  4Fe+ 3O2 → 2Fe2O3

     

    Generally metal oxides are basic in nature. But some metal oxides, such as aluminium oxide, zinc oxide show both acidic as well as basic behaviour.

     Metal oxides which react with both acids & bases to produce salts and water are known as amphoteric oxides.

     

    Aluminium oxide reacts  with acids and bases .

      

    ·         Reaction of aluminum oxide with acid forms salt and water.

     

                            Al2O3 + 6HCl → 2AlCl3 + 3H2O

     

    ·         Reaction of aluminium oxide with base forms salt and water.

     

                          Al2O3 + 2NaOH → 2NaAlO2 + H2O

     

     

    Generally, metal oxides are insoluble in water but some of these dissolve in water to form alkalis. Sodium oxide and potassium oxide dissolve in water to produce alkalis.

     

                          Na2O(s) + H2O(l) →   2NaOH(aq)

     

                          K2O(s) + H2O(l) → 2KOH(aq)

     

    Metals reaction with water 



    ·         Metals react with water and produce a metal oxide and hydrogen gas. 

     

    Metal + Water → Metal oxide + Hydrogen



    ·      Metal oxides of alkali metal that are soluble in water dissolve in it to further form metal hydroxide. 

     

    Metal oxide + Water → Metal hydroxide

     

    All metals do not react with water.



    ·         Metals like potassium and sodium react violently with cold water.  Sodium and potassium, react with water violently & evolved hydrogen immediately catch fire. It is an exothermic reaction.

                    2K(s) + 2H2O(l) → 2KOH(aq) + H2

     

     

                    2Na(s) + 2H2O(l) → 2NaOH(aq) + H2

     



    ·        Calcium and  water  reaction is less violent. The heat evolved is not sufficient for the hydrogen to catch fire.

                      Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)

     

             Calcium  floats because the bubbles of hydrogen gas formed stick to the surface of the metal.



    ·         Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen & starts floating due to the bubbles of hydrogen gas sticking to its surface.



    ·         Metals like aluminium, iron and zinc do not react either with cold or hot water.

        They react with steam to form the metal oxide and hydrogen.

                                       2Al + 3H2O → Al2O3 (s) + 3H2

                                      3Fe+ 4H2O → Fe3O4 (s) + 4H2

     

            Lead, copper, silver and gold do not react with water at all.

     

                Metals reaction with Acids

    ·        
                Metals react with acids to give salt and water       

             Metal + Dilute acid → Salt + Hydrogen

    • Reactions of magnesium, aluminum, zinc and iron with dilute hydrochloric acid.



    • When the magnesium ribbon reacts with dilute HCl, magnesium  chloride  is formed and hydrogen gas evolves. 

     

                Mg + 2HCl→MgCl2+H2



    • Similarly When the Al,Fe,zn,Ca   react with dilute HCl and form their corresponding  chloride  and  a colourless hydrogen gas evolves. 

     

                 2Al + 6HCl→2AlCl3+3H2

     

                  Zn + 2HCl→ZnCl2+H2

     

                  Fe+ 6HCl→FeCl2+H2

                  

                  Ca + 2HCl→CaCl2+H2



    • Copper don't react with dilute HCl because Cu is less reactive  than hydrogen. 

     

    Metals react with Solutions of other Metal

    Salts



    • More reactive metals can displace less reactive metals from their compounds in

                Solution or molten form.

               

         Metal (A )+ Salt solution of (B) → Salt solution of (A) + Metal (B)

     

    HOW DO METALS AND NON-METALS REA ALS REACT?



    • Reactivity of elements is due to the tendency to attain a completely filled valence shell.

     

    • A chemical bond is an interatomic attraction that holds the two atoms together. 



    • The force of attraction which holds the two atoms or ions together in a molecule is called a bond.
    •  The chemical bond may be ionic or covalent.
    • Atoms of different elements take part in chemical combinations in order to complete their octet or to attain the noble gas configuration. This is called octet rule.



    • Modes of Chemical Combination

    1.     By the transfer of electrons:

    2.     By sharing of electrons:

     

        By the transfer of electrons:



    •  Ionic or Electrovalent Bond-Ionic or Electrovalent bond is formed by the complete transfer of electrons from one atom to another.
    •  Generally, Electrovalent bonds is formed between metals and non-metals and electrostatic force of attraction which holds the oppositely charged ions together.
    •  Chemical compounds which are made up of Ionic (electrovalent) bond is known as electrovalent compounds.
    • Formation of sodium chloride

     

                               

                                  Na →Na+ + e

     

                                 (Sodium cation)

     

                                   Cl + e.  →   Cl -

                                   (Chloride anion)

     

     Sodium and chloride ions  are oppositely charged ions, They attract each other and are held by strong electrostatic forces of attraction to form Sodium chloride (NaCl). 

     

          By sharing of electrons:



    • When the bond is formed between two or more atoms by mutual contribution or sharing of electrons, it is known as covalent bond.
    • If the combining atoms are same the covalent molecule is known as homotopic. If they are different, they are known as heterotopic molecule

      

    Properties of Ionic compound:

     

    • Ionic compounds are solid. Ionic bonds have a greater force of attraction because of which ions attract each other strongly. This makes ionic compounds solid.
    • These are brittle in nature.
    • It have high melting and boiling points because force of attraction between ions of ionic compounds is very strong.
    • Ionic compounds generally dissolve in water.
    • Ionic compounds are mostly insoluble in organic solvents, like kerosene, petrol, etc.
    • In solid state , Ionic compounds do not conduct electricity . Solution of ionic compounds in water conduct electricity due to ions present in the solution of ionic compound facilitate the passage of electricity by moving towards opposite electrodes.
    • Ionic compounds conduct electricity in molten state.
    True & False test