Physical properties of metals and Non-metals-e Notes


• Metals & Non-metals. Physical properties of Metals and Non-metals. Description of physical properties of Metals and non-metals.

·                   There are 118 chemical elements known to be present till May 2011.

·                    Ununoctium is the latest element discovered in 2002.

·                   On the basis of their properties all the elements are divided into two main groups:

o       Metals

o       Non-metals.

Occurrence of Elements in Nature

·                   A large number of elements occur inside or around the earth.

·                    Less reactive elements, like platinum, gold, nitrogen, oxygen etc., occur in free (native) state.

·                   Chemically active elements always occur in the combined state i.e. in the form of compounds containing that element. They exist as fluorides, carbonates, chlorides, sulphates, sulphides.

Metals

·                   Metals are lustrous, hard, heavy and sonorous (make a ringing sound when struck).

 

Characteristics of metals:

·                   They form positive ions by loosing electrons.

·                   They are also known as electropositive elements.

·                   Example-Sodium, copper, silver aluminum etc.they form electropositive ions.

·                   The most abundant metal in the earth crust is aluminum.

·                   They are good conductors of heat and electricity.

·                   They are malleable and ductile.

Non-metals

Characteristics of Non-metals:

·                   They are generally soft, light substances and non-sonorous.

·                   They form negative ions by gaining electrons.

·                   They are also known as electronegative elements.

·                   Example- carbon, sulphur, oxygen, bromine, iodine.

·                   They do not conduct heat and electricity.

·                   They are not malleable and ductile.

·                   The most abundant non-metal in the earth crust is oxygen.

Physical Properties of Metals

Physical state:

·                   These are usually solid, except mercury, which is a liquid at room temperature.

Density:

·       They usually have high density. Iron has density of 7.8 g/cm 3.

Exception:

·                   Sodium and potassium have low density (0.97 g/cm 3 and 0.86 g/cm3.

Melting Point:

·                   They usually have a high melting point.

Example:

·                   Iron has melting point of 15350 C.

·                   Copper has melting point of 10830.

Exception:

·                   Gallium has a melting point of 32 DC

·                   Cesium has melting point of 28 DC

·                   These metals start melting in hand.

Boiling Point:

·                   Their boiling points are usually high.

Hardness:

·                   They are generally hard, except mercury, sodium, calcium, potassium, lead etc.

·                   Sodium and potassium are soft metals. They can be easily cut with knife.

Malleability and Ductility:

·                   The property which allows metals to be converted into thin sheets is called malleability.

·                   The property which allows metals to be drawn into thin wires is called Ductility.