Question

A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.

Answer 1

Part 1:

X is Carbon (C) because it is a non-metal that shows allotropy and its allotropes show the properties described.

• Allotropy: The property of an element due to which it exists in different physical forms which have identical chemical properties but different physical properties are called allotropy. The different physical forms of that element are called allotropes.
• For example, carbon is an element that shows the property of allotropy because it exists in different physical forms that have identical chemical properties but different physical properties.
• The allotropes in which the constituent particles are arranged in a particular pattern are called crystalline allotropes. Example: diamond, graphite.

Part 2:

Y is diamond because diamond is the hardest known natural substance on earth.

• Diamond exists as a giant network of carbon atoms.
• Each carbon atom is linked to four other neighboring carbon atoms i.e. each carbon atom in a diamond is tetrahedrally linked to 4 carbon atoms by a covalent bond.
• This basic tetrahedral unit repeats itself in all the directions forming a 3-dimensional (3D) network which is overall an octahedral structure (having 8 faces).
• This arrangement results in a tightly packed rigid structure. Due to this, diamond is known as the hardest naturally occurring substance.

Part 3:

Z is graphite because it is a good conductor of electricity.

• In graphite, each carbon atom is linked to 3 other carbon atoms by covalent bonds.
• Due to this, hexagonal rings are formed resulting in a 2-Dimensional (2D) sheet-like structure.
• These sheets are connected with each other by weak forces of attraction (shown by dotted lines). Due to the weak forces, these layers can slip over each other.
• As every carbon atom is linked to only three other carbon atoms, one out of the four electrons of the carbon is free i.e., not involved in bonding.
• This free electron is responsible for making graphite a good conductor of heat and electricity.