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NAVODAYA VIDYALAYA SAMITI

e content preparation

CLASS X -SCIENCE

CHAPTER NO:3

Prepared by,

DEVIKRISHNA K P

PGT CHEMISTRY

JNV DAVANGERE

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Properties of Metals

Properties

  1. Generally solids
  2. Hard
  3. Malleable and ductile(gold is the most ductile metal)
  4. Good conductors of heat and electricity (Silver & copper is the best conductor)
  5. Metallic Lusture
  6. Sonorous
  7. High m.p and b.p

Exceptions

  • Mercury is a liquid
  • Lithium , Sodium are soft

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  • Gallium and cesium have very low m.p –melts in the palm

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Properties of Non-metals

Properties

  1. Generally solids or gases
  2. Soft
  3. Brittle
  4. Bad conductor of heat and Electricity
  5. No Lusture

Exceptions

  • Bromine is a liquid
  • Diamond- an allotrope of carbon is the hardest substance

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  • Graphite is a good conductor
  • Iodine shows lusture

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Chemical Properties of Metals

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Reaction with Air/Oxygen

  • Almost all metals combine with oxygen to form metal oxides.
    • Metal + Oxygen → Metal oxide
  • metal oxides are basic in nature.
  • But some metal oxides show both acidic as well as basic behaviour-Amphoteric oxides.
    • Such metal oxides react with both acids as well as bases to produce salts and water.
      • Eg-Al2O3, ZnO

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  • Most metal oxides are insoluble in water
  • But some of the metal oxides dissolve in water to form alkalis
    • Eg-Sodium oxide , Potassium oxide

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Relative reactivity of Metals towards Oxygen

  • All metals do not react with oxygen at the same rate.
    • potassium and sodium react so vigorously that they catch fire if kept in the open.
      • Hence, to protect them and to prevent accidental fires, they are kept immersed in kerosene oil.
    • At ordinary temperature, the surfaces magnesium , aluminium, zinc, lead, etc., are covered with a thin layer of oxide.
      • The protective oxide layer prevents the metal from further oxidation.
    • Iron does not burn on heating but iron filings burn vigorously when sprinkled in the flame of the burner.
    • Copper does not burn, but the hot metal is coated with a black coloured layer of copper oxide.
    • Silver and gold do not react with oxygen even at high temperatures

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Reaction with Water

  • Metals react with water to produce a metal oxide and hydrogen
  • Metal oxides that are soluble in water dissolve to form metal hydroxide.
    • Metal + Water → Metal oxide + Hydrogen
    • Metal oxide + Water → Metal hydroxide

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Relative reactivity of Metals towards water

  • Potassium and Sodium react violently with cold water.
    • the reaction is so violent and exothermic that the evolved hydrogen immediately catches fire.
  • The reaction of calcium with water is less violent.
    • The heat evolved is not sufficient for the hydrogen to catch fire.
    • Calcium starts floating
      • the bubbles of hydrogen gas formed stick to the surface of the metal.
  • Magnesium does not react with cold water. It reacts with hot water
    • form magnesium hydroxide and hydrogen.
    • It also starts floating
  • Aluminium, iron and zinc do not react either with cold or hot water.
    • they react with steam to form the metal oxide and hydrogen.
  • lead, copper, silver and gold do not react with water

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Reaction with Acids

  • Metal + Acid → Salt + Hydrogen
  • Hydrogen gas is not evolved when a metal reacts with nitric acid.
    • It is because HNO3 is a strong oxidising agent.
    • It oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides (N2O, NO,NO2).
    • But magnesium (Mg) and manganese (Mn) react with very dilute HNO3 to evolve H2 gas.

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Reaction with Other Metal salt solution

  • A more reactive metal displaces less reactive metal from its solution
    • Metal A + Salt solution of B → Salt solution of A + Metal B
  • Displacement reaction can be used to determine the relative reactivity of Metals

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Reactivity Series

  • Metals arranged in the decreasing order of their reactivities

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Why Inert Gases are Inert?

  • The outer most shell of noble/inert gases contain 8 electrons (except He)
  • No other elements have 8 electrons in their valence shell
  • The configuration of 8 electrons is very stable which makes the noble gases inert
    • The configuration of 8 electron is known as octet
  • Atoms of other elements attains stability if they get 8 electrons in their outermost shell

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How ‘Na’ attains stability

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  • ‘Na’ will loose one electron from its outer most shell

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How ‘Cl’ attains stability

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  • ‘Cl’ will gain one electron to its outermost shell

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When ‘Na’ and ‘Cl’ react……

  • Sodium and chloride ions, are oppositely charged,
    • They attract each other
    • They are held by strong electrostatic forces of attraction to exist as sodium chloride (NaCl).
  • sodium chloride does not exist as molecules but aggregates of oppositely charged ions

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Properties of ionic compounds

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  • Physical nature
    • Solids, Hard, Brittle in nature
  • Melting and Boiling Point
    • High melting and Boiling point
  • Solubility
    • Soluble in polar solvents and insoluble in nonpolar solvents
  • Conduction of electricity
    • Conducts electricity through solution.Non conductor in solid state

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