10 Class- Metals and Non-Metals

Metals and Non-Metals

Metals

            Metals are the solid materials which are typically hard, malleable, ductile and conduct heat and electricity, and also possess metallic lusture.

Example- Iron, Gold, Aluminium, Silver, Copper etc.

Non-metals

                    Nonmetals are chemical elements which lacks metallic properties. Non metals are either solids or gases except Bromine (Br₂), which occurs as liquid. Non-metals vaporizes easily, insulator of heat and electricity. Nonmetals have high ionization energy and electronegativity values. 

Example- Hydrogen, Helium, Nitrogen, O₂, F₂, Ne, Cl, Ar, Kr, Xe, Rn, Br, C, P, S, Se, I.

Exception in metals and non-metals

·       Mercury is liquid at room temperature while other metals are solid.

·       Gallium and caesium have very low M.P. while other metals have very high M.P.

·       Iodine is non-metal but it has lustre (shiny).

·       Carbon (Non-Metal) exist in different forms, and these forms are known as allotrope.

·       Graphite (allotrope of carbon) conduct electricity and Diamond (allotrope of carbon) having very high M.P. and B.P. is hardest natural substance known.

Chemical properties of metal

Burning of metals in air

                                      Metals burn in air (as oxygen present in air) to produce metal oxide.

Metal + Oxygen -------> Metal Oxide

Example- 2Cu (Copper) + O₂ (air) ----> 2CuO (Copper Oxide)

                4Al (Aluminium) + 3O₂ --------> 2Al₂O₃ (Aluminium Oxide)

·       Mostly metal oxide is basic in nature, but some metal oxides are amphoteric in nature i.e. they show acidic as well as basic behaviour like Aluminium Oxide, Zinc Oxide.

Al₂O₃ + 6HCl --------> 2AlCl₃ + 3H₂O

    Al₂O₃ + 2NaOH -----> 2NaAlO₂ (Sodium Aluminate) + H₂O

·       Mostly metal oxide does not dissolve in water but some dissolve to form alkali.

Na₂O (s) + H₂O (l) ----------> 2NaOH (aq)

K₂O (s) + H₂O (l) ---------> 2KOH (aq)

·       Some metals prevent further corrosion by making protective oxide layer on itself like Al, Zn, Pb etc.

·       Some metals like Na, K catches accidental fire so to prevent it, they are kept fully immersed in kerosene oil.

Reaction of metals with water

                                                 Most metal react with water to form metal oxide and hydrogen gas.

Metal + Water ------> Metal Oxide + Hydrogen Gas

2K (s) + H₂O (l) --------> K₂O (s) + H₂ (g)

Not all, but some metal oxide reacts further with water to give metal hydroxide.

K₂O (s) + H₂O (l) ------> 2KOH (aq)

Some metals do not react with water like copper, lead, silver and gold.

Reaction of metals with acids

                                                 Most metal react with acids to produce salt and hydrogen gas.

Metal + Diluted Acid ---------> Salt + Hydrogen Gas

2Al + 6HCl (dil.) ----------> 2AlCl₃ + 3H₂

·       As HNO₃ is strong oxidizing agent so, hydrogen gas does not evolve when reaction take place between metal and nitric acid Because HNO₃ reduces itself to nitrogen oxides (N₂O, NO, and NO₂).

·       Aqua-Regia (Royal Water) is freshly prepared mixture of concentrated Hydrochloric Acid (Conc. HCl) and concentrated Nitric Acid (Conc. HNO₃) in the ratio of 3:1.

Aqua Regia have great dissolving power, highly corrosive, fuming liquids. Aqua Regia have ability to dissolve gold and platinum.

Reaction of metals with solution of other metal salts

                                                                                    More reactive metal has ability to displace less reactive metal from their compounds in molten or solution form.

For example, if metal A is more reactive then metal B then it displaces metal B from solution of metal B.

Metal A + Salt Solution of B ------> Salt Solution of A + Metal B

Fe (s) + CuSO₄ (aq) -----> FeSO₄ (aq) + Cu (s)

Reactivity Series of Metals

                                              Reactivity series is the series in which metals are arranged as per order of decreasing activity. This reactivity series is developed after performing so many displacement experiments. This series is also called as activity series.

K	Pottasium	More Reactive Reactivity Decreases when we move Top to Bottom Least Reactive
Na	Sodium
Ca	Calcium
Mg	Magnesium
Al	Aluminium
Zn	Zinc
Fe	Iron
Pb	Lead
H	Hydrogen
Cu	Copper
Hg	Mercury
Ag	Silver
Au	gold

How Metals react with Non-metals

                                                          As we know every element has tendency to achieve completely filled valence shell to get electronic configuration of nearby noble gas, for example a metal says sodium (Na) react with non-metal chlorine (Cl) to get complete valence shell so Na loose one electron from its outermost shell which is taken-up by chlorine (Cl), as a result they both have completely filled valence shell. In this process sodium become +vely charged and chlorine –vely charged and these charges attract each other to form NaCl.

       Na (2,8,1) --------> Na⁺ (2,8) + e^-

       Where,

                  Na⁺ is sodium cation

       Cl (2,8,7) + e^- ----------> Cl^-

       Where,

                  Cl^- is chlorine anion

Formation of Sodium Chloride

       Na⁺  + Cl^- -----------> NaCl

Properties of Ionic Compounds

                                                Ionic Compounds also called Electrovalent Compounds and their properties are described below-

1.    Physical Nature of Ionic Compounds

Ionic compounds are solid and hard due to strong force of attraction between +ve and –ve ions. Ionic compounds are also brittle.

2.    Melting and Boiling Points of Ionic Compounds

Ionic Compounds have high M.P. and B.P. as large amount of energy is needed to breakup ionic bonds.

3.    Solubility of Ionic Compounds

Ionic compounds are soluble in polar solvents like water and insoluble in non-polar solvents like ether, kerosene etc.

4.    Electric Conductivity of Ionic Compounds

Ionic compounds conduct electricity in aqueous and molten state as ions moves freely but do not conduct electricity in solid state.

Occurrence of Metals

                                              Maximum metals occur in earth’s crust and some metal occur in sea water. Metals and its compounds exist as minerals and if the percentages of metals in minerals are large then they are known as ores.

1.    Extraction of Metals

Reactivity series is very helpful in metal extraction as metals present at the bottom of reactivity series are least reactive so found in Free State like gold, silver and platinum found in Free-State. Metal at top is most reactive and metals in the middle are also reactive so found in combined form. Metals generally found as oxides, sulphides and carbonates on earth’s crust.

         

Steps involved in extraction of metals from ores-

Steps involved in Extraction of Metals from Ores

                                 

2.    Enrichment of Ore

     The process of removal of impurities or gangue from ore, before extraction of metal is known as enrichment of ore.

Gangue is terminology used for impurities like sand, soil etc. present in ore.

3.    Extracting Metals Low in Reactivity Series (or Activity Series)

                                                                                          Metals present at bottom (or low position) in activity series are very unreactive and can be obtained in pure metallic form by just heating alone.

Example- Cinnabar (HgS), ore of Mercury (Hg)

          2HgS (s) + 3O₂ (g) + heat ----------> 2HgO (s) + 2SO₂ (g)

          2HgO (s) + Heat ------------> 2Hg (l) + O₂ (g)

          Similarly,

          Cu₂S, ore of copper (Cu)

          2Cu₂S + 3O₂ (g) + Heat ----------> 2Cu₂O (s) + 2SO₂ (g)

2Cu₂O + Cu₂S + Heat ----------> 6Cu (s) + SO₂ (g)

4.    Extracting Metals in Middle of Activity Series

 Metals in middle like iron, zinc, lead etc. are moderately reactive and present as sulphides or carbonates. Metals can be easily extracted from its oxides so sulphides and carbonates are reduced to oxides. Then these metal oxides are reduced to corresponding metal by using suitable reducing agent like carbon. Chemistry Notes by Chemistry Notes Info.

Roasting

                   It is a process of converting sulphide ores into oxides by heating strongly in the presence of excess air.

          2ZnS (s) + 3O₂ (g) + Heat ---------> 2ZnO (s) + 2SO₂ (g)

          Calcination

                                It is a process of converting carbonates ores into oxides by heating strongly in the presence of limited air.

ZnCO₃ (s) + Heat ----------> ZnO (s) +CO₂ (g)

Oxide Reduction

                                 Oxides of ores are reduced to metal by using suitable reducing agent like carbon (Coke), or highly reactive metals.

ZnO (s) + C (s) ---------> Zn (s) + CO (s)

3MnO₂ (s) + Al (s) -----------> 3Mn (l) + Al₂O₃ (s) + Heat

5.    Extracting Metals at Top of Activity Series

Metals present at top in activity series are very reactive and they are not obtained by heating their compounds with carbon, for example Sodium, Calcium, Magnesium, Aluminium etc. cannot be obtained by reducing with carbon as these metals have more affinity for oxygen than carbon. So these metals are obtained by electrolytic reduction.

          In electrolytic reduction, the metals get deposited at cathode (-ve electrode) and gas like chlorine get liberated at anode (+ve electrode)

Reaction for molten Sodium Chloride-

At Cathode :-     Na⁺ + e^- --------> Na

At Anode :-       2Cl^-  -------> Cl₂ + 2e^-

Refining of Metals

                                 Refining of metals are done to obtain metals in very pure form by removing impurities present in it. Electrolytic refining is widely used method for this purpose.

Electrolytic Refining

                                      Electrolytic refining is the method of obtaining very pure metals from impure metal. Metals like copper, zinc, nickel, silver, tin, gold etc. are refined electrolytically.

In electrolytic refining, anode (+ve) is made from impure metal and cathode (-ve) is made from thin strip of pure metal. Metal salt solution works as an electrolyte. When we applied electric current across the electrodes then current starts flow through electrolytic solution. Pure metal comes out from anode and dissolve in electrolyte and equivalent amount (i.e. to that comes from anode) of this pure metal from electrolyte solution get deposited on cathode.

“In simple way we can say that pure metal come from anode and get deposited on cathode by using electrolyte solution and electric current.”

Insoluble impurities settle down below anode at bottom and we say it as anode mud, while soluble impurities mix in electrolyte.

Corrosion

                   Natural process of conversion of refined metal to its high stable form like oxides or hydroxides of metals is known as corrosion. Corrosion is the process of gradual destruction of any material like metals by environment and chemical reaction.

Example - Rusting of Iron

Prevention of Corrosion

                                                There are so many methods to prevent corrosion like-

1.    Applied Coating

                             Applied coating is surface treatment method. Planting, enamel application and painting are applied coating method to prevent corrosion. These methods create barrier between metal and environment.

2.    Anodization

                      It is anode surface treatment process in which we made thicker oxide layer at metal surface.

3.    Galvanization

                         Galvanization is the process of coating steel and iron with very thin layer of zinc to protect them from rusting.

Overall painting, greasing, oiling, chrome plating, galvanizing, alloy making and anodizing are some ways for the prevention of corrosion.