Consider the following statements regarding diamond : 1. It is an allotrope of silicon. 2. It is a bad conductor of heat and electricity. 3. Tt is the hardest substance. 4. It burns to produce carbon dioxide Which of the statements given above are correct?

Diamond is a well-known allotrope of carbon, not silicon [c2, t7]. It consists of carbon atoms arranged in a rigid three-dimensional tetrahedral lattice [t6, t8]. Regarding its physical properties, diamond is an electrical insulator (bad conductor) due to the absence of free electrons, as each carbon atom is bonded to four others [c4, t1, t10]. However, it is an exceptional thermal conductor, often exceeding metals like copper [t2, t3, t8]. Statement 2 is partially accurate in common educational contexts where 'bad conductor' often refers primarily to electricity, though technically it is a superior heat conductor. Diamond is the hardest naturally occurring substance known [c1, c2, t2]. Chemically, diamond is pure carbon and burns in the presence of oxygen at high temperatures to produce carbon dioxide gas [c3]. Therefore, statements 2, 3, and 4 are correct.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Allotropes of carbon > p. 61
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Table 3.1 > p. 40
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.3.1 Combustion > p. 69
4. [4] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Activity 11.3 > p. 179
5. [5] https://www.chm.bris.ac.uk/pt/diamond/jamessthesis/chapter1.htm
6. [6] https://en.wikipedia.org/wiki/Material_properties_of_diamond
7. [7] https://www.sciencedirect.com/topics/materials-science/natural-diamond