Question 4 of 21: Question 2, Part 2: True / False

Question 2, Part 2: True / False (8 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

4) TRUE. Atomic number (proton count) is the defining property of an element by definition – every atom of a given element has the same number of protons (isotopes vary only in neutron count).

5) TRUE. Graphite and diamond are polymorphs of pure carbon: graphite is bonded in weak, sheet-like hexagonal layers (soft, one direction of perfect cleavage), while diamond is bonded in a rigid 3-D tetrahedral network (the hardest natural mineral) – same composition, radically different structure and properties.

6) FALSE. Diamond IS a single-element mineral (pure carbon), but quartz is SiO₂ – two elements (silicon and oxygen) – so the statement that BOTH are single-element minerals is false.

7) FALSE. Lustre is classified as metallic or NON-metallic (with sub-classes such as vitreous, pearly, silky, resinous, adamantine, dull/earthy); "opaque" describes light transmission, not lustre.

8) FALSE. Colour is one of the LEAST reliable diagnostic properties because trace impurities can radically change it (e.g. quartz occurs colourless, purple, pink, smoky, yellow); hardness, cleavage/fracture, streak, and crystal habit are more diagnostic.

9) TRUE. The O²⁻ ionic radius (≈1.40 Å) is roughly 3–5 times larger than the small, highly-charged Si⁴⁺ cation (≈0.26–0.40 Å) – oxygen ions effectively define the packed framework that silicon sits inside.

10) TRUE. An isolated SiO₄ tetrahedron carries a net −4 charge (no shared oxygens); as tetrahedra polymerize (share corner oxygens) into chains, sheets, and 3-D frameworks, more of each tetrahedron's oxygens are shared between two silicons, so the net negative charge that must be balanced by other cations per silicon steadily decreases toward zero (framework silicates like quartz are electrically neutral).

11) TRUE. Calcite (CaCO₃) and dolomite (CaMg(CO₃)₂) are both carbonate minerals, built on the planar CO₃²⁻ anion group.