Question

5. Aman has read that metals are very hard but
teacher has cut one of the metals with a knife.
Name this metal.
a.) Potassium
b.) Copper
c.) Aluminium
d.) Iron ​

Answer 1

Explanation:

The bells are made by metals instead of wood because -

The metals have a unique physical property which is known as the sonorous property. Due to this property of the metals,a loud metallic sound is produced when we hit a piece of metal by any object.

Answer 2

Teacher has cut a.) Potassium metal.

Explanation:

• In general, metals are known for their hardness, sonorous, malleable and ductile property.

• But in terms of hardness, there are some exceptions. Alkali metals are an exception.

• The alkali metals are a group of chemical elements from the s-block of the periodic table with similar properties: they appear silvery and can be cut with a plastic knife.

• Potassium comes under alkali metals. Potassium is a soft, silvery metal that reacts extremely vigorously with water, and tarnishes rapidly in air.

• Alkali metals are soft mainly because of one primary reason – they have only one single electron in their valence shell and the metallic bonding is weak between the atoms.

• Hardness of a metal is determined by the strong cohesive forces between the atoms. The cohesive forces between atoms of these metals are very weak. The radius is more and there is very less force of attraction because of only one electron in outermost shell.