Why Is Mercury a Liquid?

Why Mercury Is a Liquid Metal at Room Temperature

The element mercury is a dense silvery liquid at room temperature because its valence electrons have so much energy.
The element mercury is a dense silvery liquid at room temperature because its valence electrons have so much energy. Bionerd, Creative Commons License
by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated March 08, 2017

Question: Why Is Mercury a Liquid?

Answer: Mercury is the only metal that is a liquid at normal temperatures and pressure. What makes mercury so special? Basically, it's because mercury is bad at sharing... electrons, that is.

Most metal atoms readily share valence electrons with other atoms. The electrons in a mercury atom are bound more tightly than usual to the nucleus. In fact, the s electrons are moving so fast and close to the nucleus they exhibit relativistic effects, behaving as if they were more massive than slower-moving electrons. It takes very little heat to overcome the weak binding between mercury atoms. Because of the behavior of the valence electrons, mercury has a low melting point, is a poor electrical and thermal conductor and doesn't form diatomic mercury molecules in the gas phase.