Question

The elements that are liquid at room temperature (25°C) are:

• A. bromine and chlorine
• B. helium and mercury
• C. bromine and mercury
• D. helium and chlorine

Answer 1

Answer:

C. bromine and mercury

Elements Liquid at Room Temperature

At standard room temperature and pressure (approximately 25°C or 298 K and 1 atm), only two elements are found in their liquid state.

Key Elements:

• Mercury (Hg): This is a well-known transition metal. It is often found in thermometers, barometers, and old-fashioned electrical switches due to its liquid nature and conductivity. Mercury is unique as it is the only metallic element that is liquid under standard conditions.
• Bromine (Br): This is a halogen, belonging to Group 17 of the periodic table. It is a reddish-brown, volatile liquid that readily evaporates to form a similarly colored vapor. Bromine is highly corrosive and toxic.

Important Considerations for Exams:

• Melting Points: The reason these elements are liquid is due to their relatively low melting points. Mercury's melting point is -38.83 °C, and Bromine's melting point is -7.2 °C. Both are well below the standard room temperature of 25 °C.
• Other Elements: While other elements like Gallium (Ga), Cesium (Cs), Francium (Fr), and Rubidium (Rb) have melting points close to or slightly above room temperature, they are typically solid at 25 °C. For instance, Gallium melts at around 29.76 °C, which is just above standard room temperature and can melt in your hand.
• Periodic Table Location: Knowing the location of these elements on the periodic table (Mercury in the transition metals, Bromine in the halogens) can sometimes help in recalling their properties.
• Common Misconceptions: Students might incorrectly assume other metals like Iron or Aluminum are liquid, but their melting points are significantly higher (e.g., Iron melts at 1538 °C).