Chapter 217

Metallic and non-metallic properties

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

Have you ever noticed how a hard iron object breaks easily with a light shove when it develops a red coating called rust? Or wondered where does the acid in acid rain come from? To answer all these questions, let us explore the Metallic and Non-Metallic Properties that play an important role in determining the behaviour of elements. As you have already studied, all elements can be classified into metals and non-metals, depending upon the behaviour they exhibit. In this section, let us discuss the Physical and Chemical properties of metals and non-metals.

Physical Properties of Metals

  • Metals are solid at room temperature, except mercury (Hg) and gallium (Ga), which are liquid at or near room temperature.
  • Metals are lustrous or have a shiny appearance. Owing to this, they are used extensively in jewellery and decor. Silver (Ag) is used to make mirrors as it reflects almost 90 per cent of the light falling on it.
  • Metals are hard. The hardness varies from metal to metal. Sodium (Na), Potassium (K) and Magnesium (Mg) are relatively soft and can easily be cut with a knife.
  • Metals are sonorous and produce a ringing sound when they are struck. This is why they are used to make bells, drums, etc.
  • Metals are malleable, i.e., they can be beaten into thin sheets. Gold (Au) and Silver are the most malleable. Aluminium (Al) also shows good malleability and is used as a foil to wrap food items.
  • Metals are ductile, i.e., they can be drawn into thin wires. Copper (Cu), Aluminium, Iron (Fe) and Magnesium (Mg) are commonly used to make wires.
  • Metals are good conductors of electricity. Most of the wires in our homes are made of Copper (Cu) and Aluminium (Al). Gold and Silver are used in fine electrical contacts in computers and other machines. Aluminium is used in electrical cables and Copper in appliances. Silver is the best conductor of electricity.
  • Metals are good conductors of heat. This is why water boilers and cooking utensils are made with metals like iron, copper, aluminium. Silver is the best conductor of heat.
  • Metals have high tensile strength. Thus, they can be stretched to a certain degree without breaking. Tungsten (W) has the highest tensile strength.
  • Metals have high melting and boiling points, except Caesium (Cs) and Gallium (Ga).
  • Metals are dense. Alkali metals have a relatively less density. Lithium (Li) has the lowest density and Osmium (Os), the highest.
  • Most metals are silver-grey in colour, except gold and silver.

1. Reactions of Metals with Oxygen/ Burning in air

Have you noticed that iron doors and utensils develop a red coating after some time when exposed to air and moisture? Or that magnesium ribbon burns with a white flame?

To answer why this happens, let us look at the reaction of metals with oxygen in the air.

Most metals combine with oxygen to form metal oxides. 

M + O2 → MmOn (basic),

where M is metal and MmOn is metal oxide

2Cu(s)+O2(g)→2CuO(s) [black]

When copper, a reddish brown metal, reacts with oxygen, it forms copper oxide, which is black in colour.

All metals don’t react with oxygen at the same rate. They show different behaviours as follows:

  1. Sodium (Na) and Potassium (K) react vigorously with air and catch fire. That is why they are kept immersed in kerosene oil.
    4K(s)+O2(g)→2K2O(s) (vigorous reaction)
    4Na(s)+O2(g)→2Na2O(s) (vigorous reaction)
    Here, Potassium (K) and Sodium (Na) react violently with oxygen in the air to form Potassium oxide (K2O) and Sodium oxide (Na2O), respectively.
  2. Magnesium (Mg), Aluminium (Al), Lead (Pb), Zinc (Zn) react slowly with air and form a protective layer that prevents corrosion.
    2Mg(s)+O2(g)→2MgO(s) (Mg burns with white light)
    4Al(s)+3O2(g)→2Al2O3(s)
    2 Zn(s) + O2(g)→ 2 ZnO(s) [white]
    Here, Magnesium (Mg), Aluminium (Al) and  Zinc (Zn) react with oxygen in the air to form magnesium oxide (MgO), aluminium oxide (Al2O3) and zinc oxide (ZnO), respectively.
  3. Silver (Ag), platinum (Pt) and gold (Au) do not react with air or burn even at high temperatures.
    Metal oxides are basic in nature. Most metal oxides are insoluble in water, but some of them dissolve in water to form alkalis.
    Na2O(s) + H2O(l) → 2NaOH(aq) [basic]
    K2O(s) + H2O(l) → 2KOH(aq) [basic]
    Here, sodium oxide (Na2O) and potassium oxide (K2O) react with water to form sodium hydroxide (NaOH) and potassium hydroxide (KOH), respectively.
    Some metal oxides show both acidic and basic behaviour and are called Amphoteric Oxides. Eg. aluminium oxide and zinc oxide.
    Al2O3 + 6HCl → 2AlCl3 + 3H2O
    Al2O3 + 2NaOH → 2NaAlO2 + H2O (Sodium aluminate)
    Amphoteric aluminium oxide (Al2O3) reacts with hydrochloric acid (HCl) to form aluminium chloride (AlCl3) and water. It reacts with basic sodium hydroxide (NaOH) to form sodium aluminate (NaAlO2) and water.
    ZnO(s)+2HCl(aq)→ZnCl2(aq)+H2O(l)
    ZnO(s)+2NaOH(aq)→Na2ZnO2(aq)+H2O(l) (Sodium Zincate)
    Amphoteric zinc oxide reacts with hydrochloric acid (HCl) to form zinc chloride (ZnCl2) and water. It reacts with basic sodium hydroxide (NaOH) to form sodium zincate (Na2ZnO2) and water.

 

2. Reactions of Metals with Water

Metals react with water to produce metal oxides and hydrogen gas.

M + H2O → MmOn + H2

where, M is metal and MmOn is metal oxide

Metal oxides that are soluble in water, dissolve to form metal hydroxides.

MmOn + H2O → MOH 

where, MmOn  is metal oxide and MOH is metal hydroxide

All metals react differently to water:

    1. Potassium and sodium react vigorously with cold water. In fact, the reaction is so exothermic (when heat energy is produced) and violent that the hydrogen gas produced immediately catches fire.
      2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + heat energy
      2Na(s) + 2H2O(l) → 2NaOH(aq) + H2 (g) + heat energy
      Here, Potassium (K) and Sodium (Na) react with water to form potassium hydroxide (KOH) and hydrogen gas, and sodium hydroxide (NaOH) and hydrogen gas, respectively. They are both exothermic reactions and release a large amount of heat.
    2. Calcium (Ca) on reaction with water produces heat but the reaction is not very violent as the heat produced is not sufficient for hydrogen to catch fire. In fact, calcium floats as the hydrogen bubbles stick to the metal surface.
      Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
      Here, Calcium (Ca) reacts with water to form calcium hydroxide (Ca(OH)2) and hydrogen gas.
      Magnesium (Mg) does not react with cold water but with hot water, to form magnesium hydroxide and hydrogen gas. It floats due to the hydrogen bubbles sticking to its surface.
    3. Aluminium, iron and zinc do not react either with cold or hot water. They react with steam to form their oxides and hydrogen gas. Iron, when exposed to air and moisture, develops a red-brown coating called rust, which weakens its strength.
      2Al(s) + 3H2O(g) → Al2O3(s) + 3H2(g)
      3Fe(s) + 4H2O(g) → Fe3O4 (s) + 4H2(g)
      Zn(s) + H2O(g) → ZnO(s) + H2
      Here, Aluminium (Al), iron (Fe), zinc (Zn) react with water to form aluminum oxide (Al2O3), iron oxide (Fe3O4) and zinc oxide (ZnO), respectively, along with hydrogen gas.
    4. Lead (Pb), copper (Cu), silver (Ag) and gold (Au) do not react with water at all.

3. Reaction of Metals with Acids

Metals react with acids to give salt and hydrogen gas.

M + Acid → Salt + Hydrogen gas

where, M is metal

However, not all metals react in the same way.

  1. Sodium (Na), potassium (K), lithium (Li) and calcium (Ca) react vigorously with dilute hydrochloric acid (HCl) and sulphuric acid (H2SO4) to form their metal salts and hydrogen gas.
    2Na(s)+2HCl(dilute)→2NaCl(aq)+H2(g)
    2K(s)+H2SO4(dilute)→K2SO4(aq)+H2(g)
    Here, sodium (Na) reacts with dilute hydrochloric acid (HCl) to form sodium chloride (NaCl) and hydrogen gas.
    Potassium (K) reacts with dilute sulphuric acid (H2SO4) to form potassium sulphate (K2SO4) and hydrogen gas.
  2. Magnesium, zinc, iron, tin and lead do not react vigorously with acids.
    Mg + HCl → MgCl2 + H2
    Fe + H2SO4 → FeSO4 + H2
    Here, magnesium (Mg) reacts with dilute hydrochloric acid (HCl) to form magnesium chloride (MgCl2) and hydrogen gas.
    Iron (Fe) reacts with dilute sulphuric acid (H2SO4) to form iron sulphate (FeSO4) and hydrogen gas.
  3. Magnesium and manganese react with very dilute nitric acid (HNO3) to evolve hydrogen gas.
    Mg(s)+2HNO3(dilute)→Mg(NO3)2(aq)+H2(g)
    Mn(s)+2HNO3(dilute)→Mn(NO3)2(aq)+H2(g)
    Here, magnesium (Mg) and manganese (Mn) react with dilute nitric acid (HNO3) to form magnesium nitrate (Mg(NO3)2) and manganese nitrate (Mn(NO3)2), respectively, along with hydrogen gas.
  4. Usually, when a metal reacts with nitric acid, hydrogen gas is not evolved. Because nitric acid is a very strong oxidising agent, it oxidises the evolved hydrogen gas to water and gets reduced to any of the nitrogen oxides (N2O, NO, NO2).
  5. Metals which lie below hydrogen in the reactivity series do not react with dilute acids. This is because they cannot displace hydrogen to form a bond with the non-metal anion.

4. Reaction of Metals with Solutions of other Metal Salts

When a more reactive metal displaces a less reactive metal from its salt solution, the reaction is called a Displacement reaction.

Metal M + Salt solution of N → Salt solution of M + Metal N 

Fe(s)+CuSO4(aq)→FeSO4(aq)+Cu(s)

Cu(s)+2AgNO3(aq)→Cu(NO3)(aq)+2Ag(s)

Here, in the first equation, iron (Fe) is more reactive than copper (Cu) so it displaces copper from copper sulphate (CuSO4) to form iron sulphate (FeSO4). In the second equation, copper (Cu) is more reactive than silver (Ag) and thus is able to displace it from silver nitrate (AgNO3) to form copper nitrate (Cu(NO3)).

The reactivity series is an arrangement of metals in the order of their decreasing activities.

 

Potassium (K) Increasing reactivity
Sodium (Na)
Lithium (Li)
Calcium (Ca)
Magnesium (Mg)
Aluminium (Al)
Carbon (C)
Zinc (Zn) 
Iron (Fe)
Hydrogen (H)
Copper (Cu)
Silver (Ag)
Gold (Au)

Physical Properties of Non-Metals

  • Most Non-Metals are gaseous or solid at room temperature, except bromine (Br), which is liquid. 
  • Non-Metals are not lustrous. Iodine (I) and carbon (in the form of diamond and graphite) have a shiny appearance.
  • Non-Metals are soft and brittle. The solid non-metals can be broken down in powdery substances. Eg. sulphur. Diamond, a form of carbon, is the hardest material on earth.
  • Non-Metals are not sonorous. They do not produce a ringing sound when struck with a hammer.
  • Non-Metals are not malleable, i.e., they cannot be beaten into thin sheets.
  • Non-Metals are not ductile, i.e., they cannot be drawn into thin wires.
  • Non-Metals are bad conductors of heat and electricity. Graphite, a form of carbon, is a good conductor of heat and electricity.
  • Non-Metals have low tensile strength. Carbon, in the form of diamond and graphene, has high tensile strength.
  • Non-Metals have low melting and boiling points, except diamond and graphite.
  • Non-Metals have low density.

Chemical Properties Of Non-Metals

1. Reaction of non-metals with oxygen

Non-metals react with oxygen to form acidic or neutral oxides.

S(s) + O2(g) → SO2(g)

Here, sulphur (S) reacts with oxygen to form sulphur dioxide (SO2)

Some non-metal oxides react with water to form acids. This is one of the reasons for acid rains.

SO2(g) + H2O(l) → H2SO3(aq) 

Here, sulphur dioxide (SO2) reacts with water to form sulphurous acid (H2SO3)

2. Reaction of non-metals with water

Non-metals do not react with water or steam to form hydrogen gas.

3. Reaction of non-metal with acids

Non-metals do not react with acids as when a substance reacts with acids it has to give electrons to the positive hydrogen ions produced by acids. However, non-metals are electron acceptors and not donators.

4. Reaction of non-metal with Salt Solution

Non-metals do not react with salt solutions but displace the less reactive non-metal from the salt.

Property Metals Non-Metals
Nature Electropositive Electronegative
Physical State at room temperature Solid (except Gallium and Mercury) Gas or Solid (except Bromine)
Structure Crystalline Amorphic
Appearance Lustrous or shiny Non-lustrous or dull
Density High density Low density
Malleability Malleable Non-malleable
Ductility Ductile Non-ductile
Hardness Hard (except sodium, potassium) Soft (except diamond)
Sonorous Sonorous Non-Sonorous
Melting and Boiling point High Melting and Boiling point Low Melting and Boiling point
Conduction Good conductor of heat and electricity Poor conductor of heat and electricity
Oxygen React to form basic oxides React to form acidic oxides
Acids React to form hydrogen gas Do not usually react

Everything around us is made of metals or non-metals. The elements that show properties of both metals and non-metals are called metalloids. Eg. silicon, germanium, etc. We hope that you now have a better understanding of metallic and non-metallic properties.

  • What are metallic properties?
    Metallic properties show the behaviour of metals, including how they react. Most common metallic properties are electropositivity, ductility, malleability, high melting and boiling points.
  • What are the 5 metallic properties?
    Ductility, malleability, high melting and boiling points, good conductors of heat and electricity and lustre.
  • What is the metallic property in the periodic table?
    In the periodic table, electropositivity is the metallic property.
  • Which is the least metallic metal?
    Beryllium (Be)
  • Which group has the least metallic character?
    Group 17

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