Which of the following statements is INCORRECT?

I. All the non-metals are solids at room temperature

II. Graphite is the hardest non-metal.

III. Non-metals are not sonorous.

IV. Non-metals are lustrous.

The correct answer is Option 2: I, II and IV only.

Key Points

• Statement I: It is incorrect because not all non-metals are solids at room temperature. For example, bromine is a liquid, and oxygen and nitrogen are gases at room temperature.
• Statement II: It is incorrect because graphite is not the hardest non-metal; diamond, an allotrope of carbon, is the hardest known substance.
• Statement IV: It is incorrect because most non-metals are not lustrous. However, iodine is an exception as it displays a shiny appearance.
• Statement III: It is correct because non-metals are not sonorous; they do not produce a ringing sound when struck.

Additional Information

• Non-metals:
  • Non-metals are elements that lack metallic properties such as conductivity, malleability, and ductility.
  • They are generally poor conductors of heat and electricity and are brittle in solid form.
  • Examples include oxygen, sulfur, nitrogen, and phosphorus.
• Graphite vs Diamond:
  • Graphite and diamond are both allotropes of carbon but differ in structure and properties.
  • Graphite is soft, slippery, and a good conductor of electricity, whereas diamond is extremely hard and an excellent insulator.
• Sonorous Materials:
  • Sonorous materials produce a ringing sound when struck. This property is characteristic of metals, not non-metals.
  • Examples of sonorous metals include copper, iron, and silver.
• Lustrous Non-Metals:
  • Most non-metals are dull, but exceptions like iodine and graphite exhibit a shiny appearance.
  • Luster in non-metals is typically due to their molecular structure and electronic configuration.