Class 10 Properties of metals and non-metals

### Topics to be covered

=> General introduction
=> Physical properties of metals
=> Physical properties of non-metals
=> Exceptions among metals and non-metals

### INTRODUCTION

color{green}(★) Elements can be classified as metals and non-metals.

color{green}(★) Examples of metals are: Aluminium, sodium, magnesium etc.

color{green}(★) Examples of non-metals are: Nitrogen, hydrogen, sulphur etc.

### PHYSICAL PROPERTIES OF METALS

color{green}(★) Metals, in their pure state, have a shining surface. This property is called metallic lustre.

color{green}(★) Metals are generally hard. The hardness varies from metal to metal.

color{green}(★) Metals can be beaten into thin sheets. This property is called malleability.For eg. gold and silver are the most malleable metals.

color{green}(★) Metals can be drawn into thin wires. The ability of metals to be drawn into thin wires is called ductility. Gold is the most ductile metal. A wire of about 2 km length can be drawn from one gram of gold.

color{green}(★) It is because of their malleability and ductility that metals can be given different shapes according to our needs.

color{green}(★) Metals are good conductors of heat and have high melting points. The best conductors of heat are silver and copper. Lead and mercury are comparatively poor conductors of heat.

color{green}(★) Metals are good conductors of electricity also.

color{green}(★) The metals that produce a sound on striking a hard surface and are said to be sonorous.

color{green}(★) Most metals, give rise to basic oxides when dissolved in water.

### PHYSICAL PROPERTIES OF NON-METALS

color{green}(★) The non-metals are either solids or gases except bromine which is a liquid.

color{green}(★) They do not have shining property except iodine.

color{green}(★) They are generally soft except diamond which is the hardest substance.

color{green}(★) They are non-malleable.

color{green}(★) They are non-ductile.

color{green}(★) They are poor conductors of heat and electricity except graphite.

color{green}(★) They are not sonorous.

color{green}(★) Most non-metals produce acidic oxides when dissolve in water.

### EXCEPTIONS AMONG METALS AND NON-METALS

color{green}(★) All metals except mercury exist as solids at room temperature. Metals have high melting points but gallium and caesium have very low melting points. These two metals will melt if you keep them on your palm.

color{green}(★) Iodine is a non-metal but it is lustrous.

color{green}(★) Carbon is a non-metal that can exist in different forms. Each form is called an allotrope. Diamond, an allotrope of carbon, is the hardest natural substance known and has a very high melting and boiling point. Graphite, another allotrope of carbon, is a conductor of electricity.

color{green}(★) Alkali metals (lithium, sodium, potassium) are so soft that they can be cut with a knife. They have low densities and low melting points.