Chapter at a Glance
1. Metals and non-metals: There are more than 114 elements present in the periodic table. These elements can be broadly classified into two categories i.e., metals and non-metals. Out of 114 elements, 22 are non-metals.
(i) Metals: The elements possessing characteristic properties such as lustre, malleability, ductility, thermal and electrical conductivity, high tensile strength are called metals, e.g., sodium, aluminium, iron, etc.
(ii) Non-metals: The elements which are brittle, non-lustrous and are bad conductors of heat and electricity are called non-metals, e.g., phosphorus, sulphur, oxygen etc.
2. Chemical properties of metals
(i) Reaction of metals with acids: Acids react with most metals to form a salt and hydrogen gas.
E.g., when zinc reacts with dilute sulphuric acid it gives zinc sulphate and liberates hydrogen gas
(ii) Reaction of metal with solutions of other metal salts: Some metals are more reactive than others. Such metals can displace less reactive metals from their compounds in solution or molten state. This is because highly reactive metals loses electrons easily.
In this reaction, Zn being more reactive than copper displaces it from its salt aqueous solution.
3. The reactivity or activity series : The relative electron releaseing tendencies of some metals are summed up in the activity series also called reactivity series.
(i) Active metals: Metals above hydrogen in the activity series give out hydrogen gas on reaction with a dilute acid such as HCl, 1½SO4 etc.
These are called active metals.
(ii) Inactive metals: Metals placed below hydrogen in activity series do not evolve hydrogen on reaction with dilute acids. These are considered inactive metals.
(iii) Noble metal: Metals like gold and platinum placed at the bottom of activity series are known as noble metals and they are chemically very little reactive.
(iv) Reaction with oxygen (formation of oxides): Many metals bum in the oxygen of the air to produce a metal oxide.
Metal + Oxygen —-> Metal oxide
4. Nature of metal oxides : The nature of metal oxides can be predicted from
their reactivity towards water as well as acids.
(i) Action of metal oxide with water: Oxides of some metals (i.e. Na, K, Mg etc.) dissolve in water to yield soluble hydroxides known as alkalies, e.g.,
(ii) Action of metal oxide with acids: Metal oxides react with acids to form corresponding salts and water, e.g.,
(iii)The oxides which exhibit the characteristics of both acids and bases are known as amphoteric oxides, e.g., Zn0, Al203 etc.
5. Formation and properties of ionic compounds: An ionic bond is formed with
transfer of electrons from metal to non-metal.
(i) Ionic compounds:The compounds which contain ionic bonds are called ionic compounds or electrovalent compounds. e.g. NaCl (sodium chloride).
(a) Characteristics of ionic compounds:
•They conduct electricity in aqueous solution as well as in molten state.
•They have high melting points and boiling points.
•They are highly soluble in water and are insoluble in solvents such as benzene, ether, petrol, kerosene oil etc.
•They are crystalline solids and hard because of strong force of attraction between positive ions (cations) and negative ions (anions).
6. Occurrence of metals: Major source of metals is earth’s crust, but metals also exist in sea water as their soluble salts. Metals exist both in free state or
native state (Au, Ag) and also in combined state (e.g., Na as NaCl, Fe as Fep3, Cu as Cu2S etc.)
(i) Minerals: The inorganic elements or compound which occur naturally in earth’s crust are called minerals.
(ii) Ores: Those minerals from which the metal can be extracted profitably and conveniently are called ores.
(iii) Gangue or matrix: The unwanted impurities of sand and rocky materials present in the ore is known as gangue or matrix.
7. Metallurgy: It is the branch of science which deals with the extraction of metals from their ores, and then refining them for use.
Steps involved in metallurgy:
(i) Enrichment or concentration of ore: Ores are solid material from which a pure metal can be obtained. The process of removal of unwanted material from the ore is known as concentration of ore.
(ii) Reduction: The reduction of metals are the reactions used to obtain metals from their oxides by using substances having greater affinity for oxygen than the metal.
(iii) Refining: The process of purifying impure metal is called refining of
8. Extraction of a metal: The metal at the top is most reactive and those placed at the bottom are least reactive. Metals at the middle of the series are of medium reactivity. Reactive metals (i.e., metals at the top of the reactivity series) occur in the combined state whereas least reactive metals (i.e., metals near the bottom) are generally found in the native state. Because of a difference in reactivities, different techniques are used for extracting these three different categories of metals.
9. Corrosion of metals: Corrosion is an oxidation reaction with atmospheric oxygen in the presence of water on the surface of a metal. Rusting is
i.e., rust is hydrated iron 2 (III) oxide.
10. Prevention of corrosion:
(i) Application of paint: Iron and steel (alloy of iron) are most easily protected by paint which provides a barrier between the metal and air/water. Moving parts of machines can be protected by a water-repellent oil or grease layer.
(ii) Alloying: Iron or steel along with other metals can also be protected by ‘alloying’ i.e., mixing with other metals (e.g., chromium) to make non rusting alloys.
(iii) Galvanizing: Coating iron or steel with a thin zinc layer is called ‘galvanizing
- Class 10 Notes
- Class 10 Science Notes
- NCERT Solutions for class 10th Science Chapter 3 Metals and Non-Metals