Which metal is described as a liquid at normal temperatures with a boiling point of 357°C and is highly toxic if inhaled or ingested?

• A. Gallium
• B. Sodium
• C. Aluminum
• D. Mercury

Answer: (D)

Mercury is the metal that is a liquid at room temperature and has a boiling point around 357°C. This combination is distinctive among common metals: most metals are solid at ordinary temperatures, but mercury remains liquid, which is why it’s been used historically in thermometers and other devices. The low boiling point means mercury can form vapors fairly readily, so inhaling mercury vapor or ingesting contaminated material can be highly toxic, affecting the nervous system, kidneys, and other organs.

The other metals don’t fit the description. Gallium is solid at room temperature and only becomes liquid very close to or above room temperature; its boiling point is over 2,000°C, so it doesn’t behave as a liquid under normal conditions. Sodium and aluminum are solid at room temperature as well, with much higher boiling points and different safety profiles, so they don’t match the “liquid at normal temperatures and highly toxic if inhaled or ingested” phrase.