Science (086) — AI-generated practice question

The two exceptions — iodine being lustrous and graphite conducting electricity — show that physical properties alone are not reliable for classifying elements as metals or non-metals.

Lustre (shiny surface) is generally considered a property of metals, yet iodine, a non-metal, is lustrous. Similarly, non-metals are generally bad conductors of electricity, yet graphite (an allotrope of carbon) conducts electricity. These exceptions prove that physical properties have limitations and can be misleading.

Therefore, chemical properties provide a more accurate and reliable basis for classifying elements as metals or non-metals.

Source: Chapter 3, Section 3.1.2 (Physical Properties — Non-metals)

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• Examiners expect you to name both exceptions clearly, explain what rule each one breaks, and then give the conclusion that chemical properties are more reliable.
• The textbook explicitly states: "we cannot group elements according to their physical properties alone, as there are many exceptions." Use this idea directly.
• Don't just list facts — connect them to what they tell us (the reliability question), since that is exactly what the question asks.