Metallurgy

✓physical properties of metals

✓chemical properties of metals

✓physical properties of nonmetals

✓chemical properties of nonmetals

✓reactivity series of metals

✓ ionic compounds and their physical properties

Earth was born about 4.5 billion years ago. Various formative processes have been taking place in the core of the earth and its surroundings since its creation till today. These have resulted in the formation of various ores liquids and gases.

         In the beginning, elements were classified in accordance with their chemical and physical properties into the types of metals, nonmetals and metalloids. This classification of elements is used even today. We are going to get more information about them.

Physical properties of metals

1. Metals are generally found in solid state ( except Mercury and gallium which exist in liquid state at room temperature)

2. Metals have a luster.

3. Metals are good conductors of heat and electricity.

4. Metals have high melting and boiling points.

5. Metals can be beaten into a thin sheet. This property is called as malleability.

6. Metals can be drawn into their thin wires. This property is called as ductility.

7. Metals are sonorous.

Physical properties of nonmetals

1. Under ordinary conditions, non-metals may be solids or gases. (exception bromine is in liquid state)

2. Non metals do not have metallic lustre.  (exception iodine and diamond)

3. Non metals are not ductile and malleable.

4. Non metals are bad conductor of heat and electricity. (Graphite is a good conductor of electricity though it is non metal)

5. The melting and boiling points of nonmetals are low.

Chemical properties of metals

Metals are reactive. They have one, two or three electrons in their valence shell so they easily lose electrons and become positively charged ions. That's why metals are called electropositive elements.

Reactions of metals

a. Reaction of metals with oxygen

                          Metals combine with oxygen on heating in air and metal oxides are formed.

Metal + Oxygen =>  Metal oxide

1. When sodium metal is exposed to air it readily combines to form sodium oxide.

              Na + O2       =>        Na2O

2. when magnesium is burnt in air forms magnesium oxide.

               Mg + O2     =>         MgO

b. Reaction of metals with water

1. Reaction with Na and K

Sodium and potassium metal react rapidly and vigorously with water and liberate hydrogen gas. This is an exothermic reaction.

2Na + H2O  =>  2NaOH +  H2  +  Heat

2K + H2O   =>    2KOH   +   H2 + Heat

2. Reaction with calcium

Calcium reacts with water slowly and less vigorously.

2Ca + 2H2O  => 2Ca(OH)2 + HEAT

3. Aluminium, iron and Zinc do not react with cold or hot water but they react with steam to form their corresponding oxide. Hydrogen gas is liberated in the reaction.

2Al + 3H2O    =>  Al2O3 + 3H2

3Fe + 4H2O      =>   Fe3O4 + 4H2

Zn + H2O        =>    ZnO + H2

c.  Reaction of metals with acids 

Most of the metals react with acids to form their corresponding salt and hydrogen gas is liberated.

When the metals like aluminium, magnesium, iron or zinc are reacted with dilute sulphuric acid or hydrochloric acid, sulphate or chloride salt of metals are formed. Hydrogen gas is liberated in this reaction. The reactivity of metal can be represented as follows

         Mg > Al > Zn > Fe

Mg + 2HCl     =>     MgCl2 + H2

2Al + 6HCl     =>   2AlCl3 + 3H2

Fe  + 2HCl      =>    FeCl3 + H2

Zn + 2HCl.     =>     ZnCl2 + H2

d. Reaction of metals with nitric acid

When copper is treated with concentrated and dilute nitric acid gives different products.

Nitric acid reacts with copper according to the reaction: ...

 4 HNO₃(l) + Cu(s) ==> Cu(NO₃)₂(s) + 2 NO₂(g) + 2 H₂O(l) The copper nitrate salt that forms is a deep blue color. The nitrogen dioxide is a maroon vapor.

e. Reaction of metals with salt of other metals

When iron is reacted with copper sulphate solution iron displaces copper from copper sulphate solution. 

       Fe + CuSO4 ==> FeSO4 + Cu

In this reaction the deep blue colour of copper sulphate solution turns green due to formation of ferrous sulphate.

Reactivity series of metals

The reactivity of all the metals is not same. the arrangement of metals in the increasing or decreasing order of reactivity is called the reactivity series of metals.

According to the reactivity, metals are divided into the following groups.

1. Highly reactive metals

(Potassium, sodium, lithium, calcium)

2. Moderately reactive metals

(Magnesium, aluminium, iron, lead)

3. Less reactive metals

(Copper, Mercury, silver)

f) Reaction of metals with nonmetals

When metal is reacted with non metal the ionic compound is formed.

Example: 

When sodium is reacted with chlorine forms sodium chloride.

2Na + Cl2.    ==> 2NaCl

In this example, sodium chloride ( ionic compound) is formed because sodium loses one electron while chlorine accept one electron.

Chemical properties of nonmetals

Non metals are called as electronegative elements because they form negatively charged ions by accepting electrons.

1. Reaction of non metals with             oxygen

Non metals combine with oxygen to form their corresponding oxides. Generally oxides of nonmetals are acidic in nature but in some cases neutral oxides are also formed.

C + O2 ==> CO2 (acidic)

S + O2 ==> SO2 (acidic)

2C + O2 ==> 2CO (neutral)

2. Reaction of non metals with water

Generally non metals do not react with water (exception halogens).

Chlorine dissolves in water to give hypochlorous acid (HOCl)

Cl2 + H2O ==> HOCl +HCl

3. Reaction of dilute acid with non metals

Generally non metals do not react with dilute acids (exception halogens).

Chlorine reacts with dilute hydrochloric acid to form bromine and HCl

Cl2 + 2HBr ===> 2HCl + Br2

4. Reaction of non metals with hydrogen

Non metals react with hydrogen under certain conditions like temperature pressure and use of catalyst.

S + H2 ==> H2S (hydrogen sulphide)

N2 + 3H2 ===> NH3 (ammonia)

Ionic compounds :

        Compounds formed from cation and anion are called as ionic compounds.

The cation and anion being  positively charged, there is an electrostatic force of attraction between them. This force of attraction between cation and anion is called as the ionic bond.

General properties of ionic compounds

1. Ionic compounds are crystalline solids have a definite shape.

2. They exist in solid state and are hard.

3. they are brittle and can be broken into pieces by applying pressure.

4. They have high melting and boiling points.

5. They are soluble in water but insoluble in organic solvents like kerosene and petrol.

6. They conduct electricity in the molten state and also in an aqueous solution.

[ Generally the ionic compounds have high melting point due to following reasons:-

 1. Ionic compounds are hard due to strong electrostatic force of attraction between oppositely charged ions.

2. Due to very strong electrostatic force of attraction the cations and anions are held tightly together.

3. So large amount of energy is required to overcome this strong electrostatic force of attraction.]