Which one of the following pairs of elements is liquid at room temperature and at normal pressure ?

At room temperature (approximately 20–25 °C) and normal pressure, only two elements exist in a liquid state: mercury and bromine. Mercury (Hg) is the only metal that is naturally liquid at standard room temperature, with a melting point of -38.83 °C. Bromine (Br) is the only non-metal that exists as a liquid under these conditions, possessing a melting point of -7.2 °C. While elements like gallium (Ga) and caesium (Cs) have very low melting points (29.76 °C and 28.5 °C respectively), they are technically solids at standard room temperature and only liquefy when slightly heated or held in the palm of a hand [1]. Therefore, the pair that is liquid at room temperature and normal pressure is mercury and bromine.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Table 3.1 > p. 40