Unit 4: Metals and Non-Metals

           METALS AND NON-METALS

Elements are divided mainly into two groups on the basis of physical and chemical properties – Metal and Non-metal.

Physical Properties of Metals:

Hardness: Most of the metals are hard, except alkali metals, such as sodium, potassium, lithium, etc. Sodium and lithium are very soft metals, these can be cut using knife.

Strength: Most of the metals are strong and have high tensile strength. Because of this big structures are made using metals, such as copper and iron.

State: Metals are solid at room temperature except mercury.

Sound: Metals produce ringing sound, so, metals are called sonorous. Sound of metals is also known as metallic sound. This is the cause that metal wires are used in making musical instruments.

Conduction: Metals are good conductor of heat and electricity. This is the cause that electric wires are made of metals like copper and aluminium.

Malleability: Metals are malleable. This means metals can be beaten into thin sheet. Because of this property iron is used in making big ships.

Ductility: Metals are ductile. This means metals can be drawn into thin wire. Because of this property wires are made of metals.

Melting and boiling point: Metals have generally high melting and boiling points.

Density: Most of the metals have high density.

Color: Most of the metals are grey in color. But gold and copper are exceptions.

Chemical Properties of Metals

Reaction with oxygen: Most of the metals form respective metal oxides when react with oxygen.

Metal + Oxygen ⇨ Metal oxide

Examples:

Reaction of potassium with oxygen: Potassium metal forms potassium oxide when reacts with oxygen.

4K + O2 ⇨ 2K2O

Reaction of sodium with oxygen: Sodium metal forms sodium oxide when reacts with oxygen.

4Na + O2 ⇨ 2Na2O

Lithium, potassium, sodium, etc. are known as alkali metals. Alkali metals react vigorously with oxygen.

Reaction of metals with water:- Metals form respective metal hydroxide and evolve hydrogen gas when react with water.

Metal + Water ⇨ Metal hydroxide + Hydrogen

Most of the metals do not react with water. However, alkali metals react vigorously with water.

Reaction of sodium metal with water: Sodium metal forms sodium hydroxide and liberates hydrogen gas along with lot of heat when reacts with water.

Na + H2O ⇨ NaOH + H2

Reaction of potassium metal with water: Potassium metal forms potassium hydroxide and liberates hydrogen gas along with lot of heat when reacts with water.

K + H2O ⇨ KOH + H2

Reaction of metals with dilute acid:-Metals form respective salts when react with dilute acid.

Metal + dil. acid ⇨ Metal salt + Hydrogen

Reaction of sodium metal with dilute acid: Sodium metal gives sodium chloride and hydrogen gas when react with dilute hydrochloric acid.

2Na + 2HCl ⇨ 2NaCl + H2

Reaction of potassium with dilute sulphuric acid: Potassium sulphate and hydrogen gas are formed when potassium reacts with dilute sulphuric acid.

2K + H2SO4 ⇨ K2SO4 + H2

Metal Oxides: Chemical Properties

Metal oxides are basic in nature. Aqueous solution of metal oxides turns red litmus blue.

Reaction of metal oxides with water: Most of the metal oxides are insoluble in water. Alkali metal oxides are soluble in water. Alkali metal oxides give strong base when dissolved in water.

Reaction of sodium oxide with water: Sodium oxide gives sodium hydroxide when reacts with water.

Na2O + H2O ⇨ 2NaOH

An amphoteric substance shows both acidic and basic character. It reacts with base like acid and reacts with acid like a base.

When zinc oxide reacts with sodium hydroxide, it behaves like an acid. In this reaction, sodium zicate and water are formed.

ZnO + 2NaOH ⇨ Na2ZnO2 + H2O

Zinc oxide behaves like a base when reacts with acid. Zinc oxide gives zinc chloride and water on reaction with hydrochloric acid.

ZnO + 2HCl ⇨ ZnCl2 + H2O

Reactivity Series of Metals

The order of intensity of reactivity is known as reactivity series. Reactivity of element decreases on moving from top to bottom in the given reactivity series.

In the reactivity series, copper, gold, and silver are at the bottom and hence least reactive. These metals are known as noble metals. Potassium is at the top of the series and hence most reactive.

Reactivity of some metals are given in descending order

K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu

Reaction of metals with solution of other metal salts:

Reaction of metals with solution of other metal salt is displacement reaction. In this reaction more reactive metal displace the less reactive metal from its salt.

Metal A + Salt of metal B ⇨ Salt of metal A + Metal B

Examples: Iron displaces copper from copper sulphate solution.

Fe + CuSO4 ⇨ FeSO4 + Cu

2Al + 3CuSO4 ⇨ Al2(SO4 )3 + 3Cu

Zn + CuSO4 ⇨ ZnSO4 + Cu

Cu + 2AgNO3 + Cu(NO3)2 + 2Ag

Ag + CuSO4 ⇨ No reaction

NON-METALS

Physical properties of non-metals

Hardness: Non-metals are not hard rather they are generally soft. But diamond is exception; it is most hard naturally occurring substance.

State: Non-metals may be solid, liquid or gas.

Lustre: Non-metals have dull appearance. Diamond and iodine are exceptions.

Sonority: Non-metals are not sonorous, i.e. they do not produce a typical sound no being hit.

Conduction: Non-metals are bad conductor of heat and electricity. Graphite which is allotrope of carbon is good conductor of electricity, and is an exception.

Malleability and ductility: Non-metals are brittle.

Melting and boiling point: Non-metals have generally low melting and boiling points.

Density: Most of the non-metals have low density.

Color: Non-metals are of many colors.

Chemical properties of Non-metals;- Reaction of non-metals with oxygen: Non-metals form respective oxide when react with oxygen.

Non-metal + Oxygen ⇨ Non-metal oxide

When carbon reacts with oxygen, carbon dioxide is formed along with production of heat.

C + O2 ⇨ CO2 + Heat

Sulphur gives sulphur dioxide when react with oxygen. Sulphur caught fire when exposed to air.

S + O2 ⇨ SO2

Non-metal oxide: Non-metal oxides are acidic in nature. Solution of non-metal oxides turns blue litmus red.

Carbon dioxide gives carbonic acid when dissolved in water.

CO2 + H2O ⇨ H2CO3

Sulphur dioxide gives sulphurous acid when dissolved in water.

SO2 + H2O ⇨ H2SO3

Reaction of non-metal with chlorine:

Non metals give respective chloride when they react with chlorine gas.

Non-metal + Chlorine ⇨ Non-metal chloride

Hydrogen gives hydrogen chloride and phosphorous gives phosphorous trichloride when react with chlorine.

H2 + Cl2 ⇨ 2HCl

P4 + 6Cl2 ⇨ 4PCl3

Reaction of Metal and Non-metal

Many metals form ionic bonds when they react with non-metals. Compounds so formed are known as ionic compounds.

Ions: Positive or negative charged atoms are known as ions. Ions are formed because of loss or gain of electrons. Atoms form ion to obtain electronic configuration of nearest noble gas, this means to obtain stable configuration.

Positive ion: A positive ion is formed because of loss of electrons by an atom. Following are some examples of positive ions.

Sodium forms sodium ion because of loss of one electron. Because of loss of one electron; one positive charge comes over sodium.

Na ⇨ Na+ + e−

Similarly; potassium gets one positive charge by loss of one electron.

K ⇨ K+ + e−

Negative ion: A negative ion is formed because of gain of electron. Some examples are given below.

Chlorine gains one electron in order to achieve stable configuration. After loss of one electron chlorine gets one negative charge over it forming chlorine ion.

Cl + e− ⇨ Cl−

Similarly, fluorine gets one negative charge over it by gain of one electron forming chloride ion; in order to achieve stable configuration.

F + e− ⇨ F−

Ionic Bonds

Ionic bonds are formed because of transfer of electrons from metal to non-metal. In this course, metals get positive charge because of transfer of electrons and non-metal gets negative charge because of acceptance of electrons. In other words bond formed between positive and negative ion is called ionic bond.

Formation of sodium chloride (NaCl):

In sodium chloride; sodium is a metal (alkali metal) and chlorine is non-metal.

Atomic number of sodium = 11

Electronic configuration of sodium: 2, 8, 1

Number of electrons in outermost orbit = 1

Valence electrons = Electrons in outermost orbit = 1

Atomic number of chlorine = 17

Electronic configuration of chlorine: 2, 8, 7

Electrons in outermost orbit = 7

Therefore, valence electrons = 7

Sodium has one valence electron and chlorine has seven valence electrons. Sodium requires losing one electron to obtain stable configuration and chlorine requires gaining one electron in order to obtain stable electronic configuration. Thus, in order to obtain stable configuration sodium transfers one electron to chlorine.

After loss of one electron sodium gets one positive charge (+) and chlorine gets one negative charge after gain of one electron. Sodium chloride is formed because of transfer of electrons. Thus, ionic bond is formed between sodium and chlorine. Since, sodium chloride is formed because of ionic bond, thus it is called ionic compound. In similar way; potassium chloride (KCl) is formed.

Properties of Ionic compound:

•Ionic compounds are solid. Ionic bond has greater force of attraction because of which ions attract each other strongly. This makes ionic compounds solid.

•Ionic compounds are brittle.

•Ionic compounds 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 generally insoluble in organic solvents; like kerosene, petrol, etc.

•Ionic compounds do not conduct electricity in solid state.

•Solution of ionic compounds in water conduct electricity. This happens because 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.

Occurance and Extraction of Metals

Source of metal: Metals occur in earth’s crust and in sea water; in the form of ores. Earth’s crust is the major source of metal

Mineral: Minerals are naturally occurring substances which have uniform composition.

Ores: The minerals from which a metal can be profitably extracted are called ores.

Metals found at the bottom of reactivity series are least reactive and they are often found in nature in free-state; such as gold, silver, copper, etc. Copper and silver are also found in the form of sulphide and oxide ores.

Metals found in the middle of reactivity series, such as Zn, Fe, Pb, etc. are usually found in the form of oxides, sulphides or carbonates.

Metals found at the top of the reactivity series are never found in free-state as they are very reactive, e.g. K, Na, Ca, Mg and Al, etc.

Many metals are found in the form of oxides because oxygen is abundant in nature and is very reactive.

Extraction of Metals

Metals can be categorized into three parts on the basis of their reactivity: most reactive, medium reactive and least reactive.

Steps of Extraction of Metals

Concentration of ores: Removal of impurities, such as soil, sand, stone, silicates, etc. from mined ore is known as Concentration of Ores.

Ores which are mined often contain many impurities. These impurities are called gangue. First of all, concentration is done to remove impurities from ores. Concentration of ores is also known as enrichment of ores

Conversion of metals ores into oxides:

It is easy to obtain metals from their oxides. So, ores found in the form of sulphide and carbonates are first converted to their oxides by the process of roasting and calcination. Oxides of metals so obtained are converted into metals by the process of reduction.

Roasting: Heating of sulphide ores in the presence of excess air to convert them into oxides is known as ROASTING.

Calcination: Heating of carbonate ores in the limited supply of air to convert them into oxides is known as CALCINATION.

Reduction: Heating of oxides of metals to turn them into metal is known as REDUCTION.

Purification: Metal; so obtained is refined using various methods.

Extraction of Metals of Least Reactivity

Mercury and copper, which belong to the least reactivity series, are often found in the form of their sulphide ores. Cinnabar (HgS) is the ore of mercury. Copper glance (Cu2S) is the ore of copper.

Extraction of mercury metal: Cinnabar (HgS) is first heated in air. This turns HgS [mercury sulphide or cinnabar] into HgO (mercury oxide); by liberation of sulphur dioxide.

Mercury oxide so obtained is again heated strongly. This reduces mercury oxide to mercury metal.

2HgS + 3O2 ⇨ 2HgO + 2SO2

2HgO ⇨ 2Hg + O2

Extraction of copper metal: Copper glance (Cu2S) is roasted in the presence of air. Roasting turns copper glance (ore of copper) into copper (I) oxide. Copper oxide is then heated in the absence of air. This reduces copper (I) oxide into copper metal.

2Cu2S + 3O2 ⇨ 2Cu2O + 2SO2

2Cu2O + Cu2S ⇨ 6Cu + SO2

Extraction of Metals of middle reactivity:

Iron, zinc, lead, etc. are found in the form of carbonate or sulphide ores. Carbonate or sulphide ores of metals are first converted into respective oxides and then oxides are reduced to respective metals.

Extraction of zinc: Zinc blende (ZnS: zinc sulphide) and smithsonite or zinc spar or calamine (ZnCO3: zinc carbonate) are ores of zinc. Zinc blende is roasted to be converted into zinc oxide. Zinc spar is put under calcination to be converted into zinc oxide.

2ZnS + 3O2 ⇨ 2ZnO + 2SO2

ZnCO3 ⇨ ZnO + CO2

Zinc oxide so obtained is reduced to zinc metal by heating with carbon (a reducing agent).

ZnO + C ⇨ Zn + CO

Extraction of iron from Hematite (Fe2O3): Hematite ore is heated with carbon to be reduced to iron metal.

Fe2O3 + 3C ⇨ 4Fe + 3CO2

Extraction of Metals of high reactivity

Metals of high reactivity; such as sodium, calcium, magnesium, aluminium, etc. are extracted from their ores by electrolytic reduction. These metals cannot be reduced using carbon because carbon is less reactive than them.

Electrolytic Reduction: Electric current is passed through the molten state of metal ores. Metal; being positively charged; is deposited over the cathode.

Example: When electric current is passed through molten state or solution of sodium chloride, sodium metal deposited over cathode.

Na+ + e− ⇨ Na

2Cl− − e− ⇨ Cl2

2NaCl ⇨ 2Na + Cl2

Metals obtained from the process of electrolytic reduction are pure in form.

Refining or purification of metals:

Metals extracted from various methods contains some impurities, thus they are required to be refined. Most of the metals are refined using electrolytic refining.

Electrolytic Refining: In the process of electrolytic refining a lump of impure metal and a thin strip of pure metal are dipped in the salt solution of metal to be refined. When electric current is passed through the solution, pure metal is deposited over thin strip of pure metal; from lump of impure metal. In this, impure metal is used as anode and pure metal is used as cathode.

Corrosion:Most of the metals keep on reacting with the atmospheric air. This leads to formation of a layer over the metal. In the long run, the underlying layers of the metal keep on getting lost due to conversion into oxides or sulphides or carbonate, etc. As a result, the metal gets eaten up. This process is called corrosion.

Rusting of Iron: Rusting of iron is the most common form of corrosion. When iron articles; like gate, grill, fencing, etc. come in contact with moisture present in air, the upper layer of iron turns into iron oxide. Iron oxide is brown-red in color and is known as rust. This phenomenon is called rusting of iron.

Prevention of Rusting: For rusting, iron must come in contact with oxygen and water. Rusting is prevented by preventing the reaction between atmospheric moisture and the iron article. This can be done by painting, greasing, galvanization, electroplating, etc.

                                   TEXTUAL QUESTIONS

1. Give an example of a metal which
(i) is a liquid at room temperature. (ii) can be easily cut with a knife.

► Mercury                                                         ► Sodium

(iii) is the best conductor of heat    (iv) is a poor conductor of heat.

► Silver                                                              ► Mercury and Lead

2.Explain the meanings of malleable and ductile.
Answer-Malleable:Substances that can be beaten into thin sheets are called malleable. For example, most of the metals are malleable.
Ductile: Substances that can be drawn into thin wires are called ductile. For example, most of the metals are ductile.

1. Why is sodium kept immersed in kerosene oil?
Answer-Sodium is high reactive element. If it is kept in open it can explosively react with oxygen to catch fire. Hence to prevent accidental damage sodium is immersed in kerosene oil.
2. Write equations for the reactions of
(i) iron with steam
(ii) calcium and potassium with water
Answer-(i) 3Fe (s) + 4H2O (g) → Fe3O4 (aq) + 4H2 (g)
(ii) Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g) + Heat
      2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g) + Heat
4. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.
Answer-Hydrogen gas is evolved when dilute hydrochloric acid is added to a reactive metal.When iron reacts with dilute H2SO4, iron (II) sulphate with the evolution of hydrogen gas is formed.Fe (s) + H2SO4 (aq) → FeSO4 (aq) + H2 (g)
5. What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.

Answer-When zinc is added to iron (II) sulphate then it will displace the iron from iron sulphate solution as shown in the following chemical reaction.Zn (s) + FeSO4 (aq) → ZnSO4 (aq) + Fe (s)
1. (i) Write the electron-dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of Na2O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?
Answer-(i) The representation of elements with valence electrons as dots around the elements is referred to as electron-dot structure for elements.

(ii)

(iii) The ions present in Na2O are Na+ and O2- ions and in MgO are Mg2+ and O2- ions.
2. Why do ionic compounds have high melting points?
Answer-Ionic compounds have strong electrostatic forces of attraction between the ions. Therefore, it requires a lot of energy to overcome these forces. That is why ionic compounds have high melting points.

1. Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue

Answer-(i) Mineral: The naturally occurring compounds of elements are known as Mineral.
(ii) Ore: Minerals from which metals can be extracted profitably are known as ores.
(iii) Gangue: The impurities present in the ore such as sand, rocks etc are non as gangue.
2. Name two metals which are found in nature in the free state.
Answer-The metals at the bottom of the reactivity series are mostly found in free state. For example: gold, silver, and platinum.
3. What chemical process is used for obtaining a metal from its oxide?
Answer-A metal can be extracted from its oxide by the process of reduction.

Metal	Zinc	Magnesium	Copper
Zinc oxide	No reaction	Displacement	No reaction
Magnesium oxide	No reaction	No reaction	No reaction
Copper oxide	Displacement	Displacement	No reaction

1. Metallic oxides of zinc, magnesium and copper were heated with the following metals. In which cases will you find displacement reactions taking place?
Answer

2. Which metals do not corrode easily?
Answer-Metals which have low reactivity such as silver, gold does not corrode easily.
3. What are alloys?

Answer-An alloy is the homogeneous mixture of two or more metals or metals and non metals. For example brass is an alloy of copper and zinc.

EXCERCISE
5. You are given a hammer, a battery, a bulb, wires and a switch.

(a) How could you use them to distinguish between samples of metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Anwer-(a) With the hammer, we can beat the sample and if it can be beaten into thin sheets (that is, it is malleable), then it is a metal otherwise a non-metal. Similarly, we can use the battery, bulb, wires, and a switch to set up a circuit with the sample. If the sample conducts electricity, then it is a metal otherwise a non-metal.
(b) The above tests are useful in distinguishing between metals and non-metals as these are based on the physical properties. No chemical reactions are involved in these tests.

6. What are amphoteric oxides? Give two examples of amphoteric oxides.

Answer-Those oxides that behave as both acidic and basic oxides are called amphoteric oxides.
Examples: aluminium oxide (Al2O3), zinc oxide (ZnO)
7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Answer-Iron and aluminium will displace hydrogen from dilute acids as they more reactive then hydrogen. Mercury and copper cannot displace hydrogen from dilute acids as they are less reactive than hydrogen.
8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Answer-In the electrolytic refining of a metal M:
Anode → Impure metal M
Cathode → Thin strip of pure metal M
Electrolyte → Solution of salt of the metal M

10. State two ways to prevent the rusting of iron.
Answer-Two ways to prevent the rusting of iron are:
→ Oiling, greasing, or painting: By applying oil, grease, or paint, the surface becomes water proof and the moisture and oxygen present in the air cannot come into direct contact with iron. Hence, rusting is prevented.
→ Galvanisation:An iron article is coated with a layer of zinc metal, which prevents the iron to come in contact with oxygen and moisture. Hence, rusting is prevented.

11. What type of oxides are formed when non-metals combine with oxygen?
Answer-When non-metals are combined with oxygen then neutral or acidic oxides are formed. Examples of acidic oxides are NO2, SO2 and examples of neutral oxides are NO, CO etc.
12. Give reasons-(a) Platinum, gold and silver are used to make jewellery.

(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Answer-(a) Platinum, gold, and silver are used to make jewellery because they are very lustrous. Also, they are very less reactive and do not corrode easily.
(b) Sodium, potassium, and lithium are very reactive metals and react very vigorously with air as well as water. Therefore, they are kept immersed in kerosene oil in order to prevent their contact with air and moisture.
(c) Though aluminium is a highly reactive metal, it is resistant to corrosion. This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide. This oxide layer is very stable and prevents further reaction of aluminium with oxygen. Also, it is light in weight and a good conductor of heat. Hence, it is used to make cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because metals can be easily extracted from their oxides rather than from their carbonates and sulphides.
13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Answer-Copper reacts with moist carbon dioxide in air to form copper carbonate and as a result, copper vessel loses its shiny brown surface forming a green layer of copper carbonate. The citric acid present in the lemon or tamarind neutralises the basis copper carbonate and dissolves the layer. That is why, tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of the copper vessel its characteristic lustre.
14. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer-

Metal	Non-metal
Metals are electropositive.	Non-metals are electronegative.
Oxides of metal are basic in nature.	Oxides of non-metals are acidic in nature.
Metals displace hydrogen from dilute acids.	They can't replace hydrogen from dilute acids.
Metals form chlorides which are electrovalent or ionic compounds.	Non-metals form chlorides which are covalent compounds.
They react with water to form oxides and hydroxides. Some metals react with cold water, some with hot water, and some with steam.	They do not react with water.

15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. Can you play the detective to find out the nature of the solution he had used?
Answer-The solution he had used was Aqua regia. Aqua regia is Latin word which means ‘Royal Water’. It is the mixture of concentrated Hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It is capable of dissolving metals like Gold and Platinum. Since the outer layer of the gold bangles is dissolved in aqua regia so their weight was reduced drastically.
16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer-Copper does not react with cold water, hot water, or steam. However, iron reacts with steam. If the hot water tanks are made of steel (an alloy of iron), then iron would react vigorously with the steam formed from hot water.3Fe + 4H2O → Fe3O4 + H2O
That is why copper is used to make hot water tanks, and not steel.
1. Which of the following pairs will give displacement reactions?
► (d) AgNO3solution and copper metal.
2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
► (c) Applying a coating of zinc
3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
► (a) calcium
4. Food cans are coated with tin and not with zinc because
► (c) zinc is more reactive than tin.