Chapter 3: Metals and Non-Metals

CHAPTER→  3

METALS AND NON- METALS

 Physical properties of metals and non- metals.

 1     LUSTRE  -

→  Metals have shining surface.

  →  Non-metals do not have shinig surface

 * Except iodine   

 2 Hardness -

 →   Metals are generally hard.

• Except sodium lithium and potassium which are soft and can be cut with knife.

→ Non – metals are generally soft.

• Except diamond a form of carbon which is the hardest natural substan

3 Malleability - 

 Metals can be beaten into thin sheets gold and silver are the most malleable metals.

Non- metals are non-mallerable.

4 Ductility -

 →Metals can be drawn into thin wires.

 →Non- metals can not be drawn into thin wires. They are non- ductile.

5 Conductor of heat and electricity -

→Metals are good conductor of heat and electricity of heat. Lead and mercury are poor conductor of heat.

Metals are good conductor of heat and electricity.

→Non- metals are poor conductor of heat EXCEPT graphite.

6 state -

→ The metals exist as solids. EXCEPT mercury

→The non- metals exist as solids or gaseous.EXEPT  bromine.

7 density -

→Metals have high density and high melting point.

→Except sodium and potassium.

8 Oxides -

→ Metallic oxides are basic in nature.

→Non metallic oxides are acidic in nature.

9 Sonorous -

→Metals produce a sound on strinking a hard surface.

→Non-metals are not sonorous.

Chemical properties of Metals

(i)  Reaction with air :-

All metals combine with oxygen to form metal oxide .

Metal + O₂      →     Metal oxide

For example,

2Cu  +  O₂      →    2CUO    copperoxide (black)

 4Al + 3O₂   →     2Al₂O₃     Aliminium oxide

• Sodium and potassium react so vigorously that they catch fire in open so they are kept immersed in kerosence
• Surfaces of Mg , Al, Zn pb are covered with a thin layer of oxide whish prevent them from further oxidation. Anodizing is a process of forming a tick oxide layer of aluminium.
• Iron does not burn on heating but iron filling burn vigorously.
•  Copper does not burn but the hot metal is coated with a black coloured layer of copper (ii) oxide
• Silver and gold do not react with oxygen even at high temperatures.

Amphoteric oxide  →  Metal oxides which react with both acids as well as bases to produce salts and water are called amphoteric oxides.

Example ;   

Al₂O₃   +    6HCl   →   2AlCl₃ +   H₂O

 Al₂O₃  +  2NaOH  →  2NaAlO₂    +   H₂O

                                (SODIUM ALUMINATE )

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

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

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

(ii)  Reactions of metals with water:-

 Metal+ water  →      Metal oxide  +  hydrogen

Metal oxide  +  water   →   metal hydroxide

 Metals like potassium and sodium react violenty with cold water.

Na  +   2 H₂O     →     NaOH + H₂  + heat energy.

The reaction of calcium of water is less violent

Ca + 2H₂O    →   Ca(oH)₂ + H₂

Magnesium react with hot water to form magnesium hydroxide and hydrogen.

Mg +  2H₂O     →  Mg(OH)₂    +  H₂

Metals like aluminium iron and zinc do not react with cold or hot water. But they react with steam to form metal oxide and hydrogen.

2 Al + 3 H₂0     →    Al₂O₃  +   3H₂

3 Fe  + 4 H₂O     →  Fe₃O₄   +   4H₂

Metal such as lead ,copper, silver and gold do not react with water at all.

(ii) Reaction of metals with acids.

Metal +  Dilute acid  →   salt + hydrogen

Copper and silver do not react wit dil acids.

 For example 

 Fe +  2HCl     →     FeCl₂  +  H₂

Mg  +  2HCl     →     MgCl₂  +   H₂

Zn  +   2HCl      →     ZnCl₂  +  H₂

(iii)   Reaction of metals with solution of other Metal salts ; 

Metal A+  Salts solution B  →    Salt solution A + Metal B   

Reaction of metals with salt solutions.

More reactive metals can displace less reactive metals from their compounds in solution form.

Fe +  CuSO₄    →      FeSO₄  +    Cu       

Fe displaces Cu because Fe is more reactive metals than Cu .

REACTIVITY SERIELS ;

The reactivity series is a list of metals arranged in the order of their decreasing activities.

METALS AND NON- METALS REACTIONS

• Atoms of the metals lose electron from their valence shell to form cation.
• Atoms of the non- metals gain electrons in the valence to form anion.

Formation of sodium chloride.

Formation of magnesium chloride

Properties of ionic compound

1. PHYSICAL NATURE  :-  They are solid and hard (because of the strong force of attraction between the positive and negative ions) . They are brittle.
2. Melting and boiling point:_  They have high melting and boiling pont.
3. Solubility :- soluble in water and insoluble in solvents such as kerosene , petrol etc.
4. Conductor of electricity :- Ionic compound conduct electricity in molter (ions move to the opposite electrodes  when electricity is passed )

• They do not conduct electricity in solid state as movements of ions is not possible in solid They conduct electricity in molten state.

OCCURANCE OF METALS

MINERALS :- The elements which occur naturally in the earth’s crust are called minerals.

ORES:- Minerals that contain very high percentage of particular metal andthe metal can be profitably extracted from it, such minerals are called ores.

• Metals at the bottom of the activity series are least reactive they are often found in free state . For Example –  Ag,Au, Cu.
• Metals at the ttop of the acitivity series (k,Na, Co, Mg, and Al) are so reactive that they never found in free state.
• Metals in the middle of the activity series ( Zn, Fe,Pb etc are moderately reactive . they occur as sulphates ,oxides or carbonates.
• They ore of many metals are oxide because oxygen is very reactive and is abundant on the earth.
• Steps involved in the extraction of pure metals from ores.

 Step involved in the extraction of metals from ores.

 EXTRACTION OF METALS FROM ORES :-

 1 ENCRICHMENT OF ORES    Ores are usually contaminated with large amounts of impurities such as soil, sand etc called gangue these impuriestes are removed from the ore prior to the extraction of mertal.

 2  Extraction of metals   Metals low in the activity series are very anreactive the oxides of these metals are reduced to metals by heating.

 For example           

 2HgO   →      2Hg  +  O₂

Mercury oxide is reduced to mercury on heating

The metals in the middle of the activity series ( Zn, Fe, Pb, Cu ) are moderately active. The metal sulphides  and carbontes  are converted into metal oxide. The sulphate ores are converted into oxides by heating strongly in the presence of excess air this process is known as roasting .

2 ZnS + 3O₂ →      2ZnO + CO₂

• The carbonate ores are changed into oxides by heating strongly in limited air this process is called calcination .

 Zn CO₃     →     ZnO + CO₂

• Then metal oxides are reduced to corresponding metals by using reducing agent like carbon.

 ZnO  +  C    →   Zn   +  CO

• This reaction of iron (iii) oxide ( Fe2O3) with aluminium is used to join railway tracks or cracked machine parts . this reaction is known as thermit reaction.

 Fe₂O₃    +  2Al    →  2 Fe +  Al₂O₃ + heat

 Metals high up in the reactivity series are very reactive. The metalo are obtained by electrolytic reduction. The metals are deposit at the cathode and chlore is deposited at anode.

At cathode  →   Na⁺    +  e^-    →     Na
At anode   →     2Cl^-   →    Cl₂   +  2e^-

Refining of metals

 The most widely used method for refining impure metals is electronic refining.

Electrolytic refining :-   Metals  ( Cu, Zn , Ag, Au etc ) are refined electrolytically . the impure metal is made the anode and athin strip of pure metal is made the cathode . a solution a metal salt is used as an electrolyte.

Electrolytic refining of copper.

Anode :  Impure copper

Cathode: Strip of pure copper

The insoluble impurities settle at the bottom of the anode and is called anode mud.  

CORROSION :-

The surface of metals is corroded when they are exposed to moist air for a long period of time. This is called corrosion

For example 

• Silver becomes black when exposed to air and form a coating of silver sulphide.
• Copper react with  moist Co_{2 and form a green coat of copper carbonate.}
• Iron acquires a coating of brown floky substance called rust.

 Prevention of corrosion. 

The rusting of iron can be prevented by painting , oiling, greasing, galvanizing, chrome plating anodizing and making alloys.

• Galvanisation:-  It is a method of protecting steel and iron from ressting by coating them a thin layer of zinc.
• Alloying is a very good method of improving the properties of a metal an alloy is a homogenous mixture of two or more metals or a metal and a non- metal
• Iron  →    it is mixed with small amount of carbon
• Steel →   iron + nickel and chromium.
• Brass  → copper  + tin
• Solder   →  lead  +  tin ( used for welding electric wire together )