Mercury (Hg)
Transition metal
Mercury is the only metal liquid at room temperature — the “quicksilver” of alchemists. Once ubiquitous in thermometers and dental fillings, it is now tightly restricted because its vapour and compounds poison the nervous system.
Position on the periodic table
Atomic properties
| Atomic number | 80 |
|---|---|
| Atomic mass | 200.592 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 |
| Noble gas shorthand | [Xe] 4f14 5d10 6s2 |
| Electrons per shell | 2, 8, 18, 32, 18, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +2, +1 |
| Electronegativity (Pauling) | 2 |
| Covalent radius (approx.) | 132 pm |
| First ionization energy | 1007 kJ/mol |
| Electron affinity | -48 kJ/mol |
Physical properties
| State at 25 °C | Liquid |
|---|---|
| Density | 13.53 g/cm³ |
| Melting point | -38.83 °C (234.32 K) |
| Boiling point | 356.73 °C (629.88 K) |
| Appearance | silvery |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of mercury
Mercury's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10, usually shortened to [Xe] 4f14 5d10 6s2. Its electrons occupy 6 shells (2, 8, 18, 32, 18, 2), placing it in period 6 of the d-block. Explore it interactively in the electron configuration calculator.
Uses of mercury
- Fluorescent lamp vapour
- Industrial catalysts and electrodes (declining)
- Historic thermometers and barometers
- Small-scale gold extraction (a major pollution problem)
Biological role: None — toxic; methylmercury accumulates up the food chain into large fish.
Occurrence: Mined as cinnabar (HgS), famously at Almadén, Spain.
Common compounds of mercury
HgS
Cinnabar (mercury sulfide)
HgCl2
Mercury(II) chloride
History and discovery
Discovered: Known since ancient times — unknown, before 2000 BCE. Name origin: Named after the swift Roman god; the symbol Hg is from Greek hydrargyros, “water-silver”.
Known to ancient Egypt, India and China; Roman mines used enslaved labour to extract cinnabar for red pigment.
Safety notes
Mercury vapour and soluble compounds are highly toxic. Spilled mercury from broken devices needs proper cleanup — never vacuum it.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Mercury
1. What is the chemical symbol of Mercury?
2. What is the atomic number of Mercury?
3. Which category does Mercury belong to?
4. What is the state of Mercury at room temperature?
5. Which period of the periodic table is Mercury in?
Mercury FAQs
What is the atomic number of mercury?
Mercury's atomic number is 80 — every mercury atom has 80 protons in its nucleus.
What is the symbol for mercury?
Hg. Named after the swift Roman god; the symbol Hg is from Greek hydrargyros, “water-silver”.
Is mercury a metal, nonmetal, or metalloid?
Mercury is classified as a transition metal.
What state is mercury at room temperature?
At about 25 °C, mercury is a liquid. It melts at -38.83 °C.
What is mercury used for?
Key uses include: fluorescent lamp vapour; industrial catalysts and electrodes (declining); historic thermometers and barometers.
Related elements
Keep working with this element
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