Science — CBSE Class 10 board question

(i) Low melting and boiling points: Carbon compounds are covalently bonded. Although the bonds within the molecule are strong, the intermolecular forces between molecules are very weak. Therefore, less energy is required to overcome these forces, resulting in low melting and boiling points.

(ii) Do not conduct electricity: In covalent compounds, electrons are shared between atoms rather than transferred. No charged particles (ions) are formed. Since there are no free ions or electrons to carry charge, carbon compounds are poor conductors of electricity.

(iii) Only covalent compounds: Carbon has 4 valence electrons. To form C⁴⁻, its nucleus (6 protons) cannot hold 10 electrons; to form C⁴⁺, removing 4 electrons requires too much energy. So carbon overcomes this by sharing electrons, forming only covalent bonds.

Source: Chapter 4, Section 4.1 – Bonding in Carbon: The Covalent Bond

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• All three parts are directly from Section 4.1. Examiners expect you to link the property back to the covalent bond nature.
• For (i): Key phrase is "strong intramolecular bonds but weak intermolecular forces."
• For (ii): Key phrase is "sharing of electrons → no ions formed → poor conductor."
• For (iii): You must give both reasons (why it can't gain AND why it can't lose electrons) to get full credit — one reason alone is incomplete.