Mercury (element) - Wikipedia Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver and was formerly named hydrargyrum (/ h aɪ ˈ d r ɑːr dʒ ər ə m / hy-DRAR-jər-əm) from the Greek words, hydor (water) and argyros (silver). A heavy, silvery d-block element, mercury is the only metallic element that is known to be liquid at standard conditions for …