Basic concepts of NCERT Class 10 chapter 3— Metals and Non-metals

The most important points of Metals and Non-metals

1. Metals are lustrous, malleable and ductile and possess high density. They are good conductors of heat and electricity.

2. Metals are solids at room temperature, except Mercury which is a liquid.

3. Metals are generally hard. The hardness varies from metal to metal. Sodium, potassium are soft that these can be cut with a knife.

4. Metals are also called electropositive elements.

5. Metals form basic oxides.

6. Reactive metals can displace less reactive metals from their compounds in solution or molten form. Based on this, metals can be arranged in order of decreasing reactivity which is known as activity series as given.

K >Na>Ca>Mg>Zn>Fe>Pb>H>Cu>Hg>Ag>Au.

Thus metals above H in the activity series will replace H2 from dilute acids.

7. Metals combine with  Non-metals to form ionic compounds. Metals lose electrons and Non-metals gain electrons in the formation of ionic compounds. For example, sodium chloride, magnesium oxide and aluminium chloride. These are solids and are generally soluble in water. These do not exist as single molecules but as a network of ions in which each cation is surrounded by a given number of anions and vice-versa.

8. Metals occur in nature as free elements or as compounds in the form of ores.

9. Ores mined from earth usually contain unwanted material called gangue. This is removed by treatments like hydraulic washing, magnetic separation, froth flotation etc. This is called enrichment of ores.

10. It is easier to obtain metals from their oxides than from their sulphides or carbonates. Sulphides are converted into oxides by roasting (heating in air) and carbonates into oxides by calcination (heating in absence of air).

11. Pure metal is obtained by reduction with carbon or aluminium. Highly reactive metals like Na, Mg, Al are obtained by Electrolytic Reduction. Metals low in reactivity, e.g., Mercury can be reduced by heating their compounds.

12. Metals find extensive use as alloys. An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal. An alloy is prepared by mixing the metal with another metal or non-metal in the molten state and then cooling them to room temperature. This gives improved properties to Metals such as better resistant to corrosion, hardness etc.

13. Corrosion is a phenomenon wherein a metal such as iron is damaged when exposed to moisture. Corrosion of metals can be prevented by various methods such as painting, oiling, greasing, galvanizing and electroplating.

14. There are twenty two non metals. Eleven are gases, ten are solids and one (bromine) is a liquid.

15. Non-metals are usually brittle. They do not form sheets or wires and are non-conductors of heat or electricity except carbon in the form of graphite. These form acidic oxides. 

16. Non-metals do not displace Hydrogen from Dilute acids. These generally form covalent compounds with Hydrogen, oxygen and Chlorine.