Name the black substance of pencil. Will the current flow through the electrical circuit when we use the sharpened ends of the pencil to complete the circuit?

Give a reason why carbon can neither form C^{4 +} cations nor C^4— anxious, but forms covalent compounds which are bad conductors of electricity and have low melting and boiling points.

(i) Name the bond formed when X₇¹⁴ combines with Y₉¹⁸ .

(ii) Write the chemical formula of the compound formed when X₇¹⁴ combines with Y₉¹⁸ .

What type of bond is present in F₂?

(a) Name the element E.

(b) What is allotrope A?

(c) What is allotrope B?

(d) What is allotrope C?

(e) Which allotrope is used in making jewellery?

(f) Which allotrope is used in making anode of a dry cell?

(a) What is element A?

(b) What is the gas B?

(c) Name the allotrope C.

(d) State another use of allotrope C (other than in glass cutters)

(e) Name another allotrope of element A which exists as spherical molecules.

(f) Name a yet another allotrope of element A which conducts electricity.

What are hydrocarbons? Give examples.

State the reason why carbon can neither form C⁴⁺ cations nor C^4- anions, but forms covalent compounds. Also state reasons to explain why covalent compounds:

(a) are bad conductors of electricity?

(b) have low melting and boiling points?

Unsaturated hydrocarbons contain multiple bonds between the two C atoms and show addition reactions. Give the test to distinguish ethane from ethene.

Catenation is the ability of an atom to form bonds with other atoms of the same element. It is exhibited by both carbon and silicon. Compare the ability of catenation of the two elements. Give reasons.

The heteroatoms present in CH₃ — CH₂ — O — CH₂ — CH₂Cl are

(i) oxygen

(ii) carbon

(iii) hydrogen

(iv) chlorine