Mercury

Mercury is atom number 80 — every Mercury atom has exactly 80 protons in its center, and that number is what makes it Mercury and nothing else. Its symbol is Hg. At room temperature it is a liquid.

Mercury is a chemical element with symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum (/haɪˈdrɑːrdʒərəm/). A heavy, silvery d-block element, mercury is the only metallic element that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature.

Summary from the source dataset, derived from Wikipedia (CC BY-SA 3.0) · original article

Mercury sits in period 6, group 12 of the d-block. Its 80 electrons fill shells of 2, 8, 18, 32, 18, 2 — written as [Xe] 4f14 5d10 6s2. Its electronegativity is 2 on the Pauling scale, and pulling the first electron off takes 1007.1 kJ/mol. The outermost shell holds 2 electrons — the ones that do all the chemistry.

Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10
Ionization energies (kJ/mol): 1007.1, 1810, 3300
Electron affinity: -48 kJ/mol · Electronegativity (Pauling): 2
Density: 13.534 g/cm³ · melts 234.321 K · boils 629.88 K

Values exactly as published — see where the data comes from.