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Q4 (CDS-II/2008) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic chemical principles Answer Verified

Which one of the following is an element ?

Result
Your answer: —  Â·  Correct: B
Explanation

An element is a substance consisting of only one type of atom [t6]. Diamond is an allotrope of carbon, meaning it is a distinct physical form of the pure element carbon [c2][t5]. In diamond, each carbon atom is bonded to four other carbon atoms in a rigid three-dimensional tetrahedral structure [c1][t4]. Because it is composed entirely of carbon atoms, it is classified as an element [t6][t7]. In contrast, the other options are chemical compounds. Ruby and sapphire are both varieties of the mineral corundum, which is chemically aluminium oxide (Al2O3) [t1][t2]. Topaz is a complex mineral classified as an aluminium silicate containing fluorine, with the chemical formula Al2(F,OH)2SiO4 [t2]. Therefore, only diamond represents a pure elemental form.

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
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