The correct option is Iodine.
Explanation
Metals are generally characterized by a lustrous (shiny) appearance, whereas non-metals typically exhibit a dull surface. However, there are specific exceptions where non-metals display physical properties usually associated with metals.Detailed Analysis:
- Iodine: Iodine is a non-metal that exists as a solid at room temperature. It is a notable exception to the general rule because it possesses a natural metallic lustre, appearing as shiny, purple-black crystals.
- Sulphur: This non-metal typically appears as a yellow solid or powder with a dull, non-reflective surface.
- Phosphorus: Phosphorus exists in various allotropic forms (such as white, red, and black phosphorus). These forms generally have a waxy or dull appearance rather than a lustrous one.
- Bromine: Bromine is unique as the only non-metal that is liquid at room temperature. It appears as a reddish-brown liquid and does not exhibit the crystalline lustre found in Iodine.
Key Takeaway:
While non-metals are generally dull, Iodine and Graphite (an allotrope of Carbon) are specific exceptions that possess a lustrous appearance.