Mercury (Hg)
Element 80 · Transition metal · atomic mass 200.59 u · group 12, period 6
Electron shells: 2, 8, 18, 32, 18, 2
Mercury is the only metal that is liquid at room temperature, which made it the heart of thermometers and barometers for centuries. Its toxicity has now driven it out of almost every consumer product.
"Mad as a hatter" was literal — hat makers using mercury to treat felt suffered severe neurological damage.
- Atomic number
- 80
- Atomic mass
- 200.59 u
- Electron configuration
- [Xe] 6s² 4f¹⁴ 5d¹⁰
- Group · period · block
- 12 · 6 · d
- Oxidation states
- +1, +2
- Electronegativity
- 2 (Pauling)
- Melting point
- -38.83 °C
- Boiling point
- 357 °C
- Density
- 13.5336 g/cm³
- State at 20 °C
- Liquid
- Appearance
- Silvery liquid metal
- Discovered
- Known since antiquity
80 protons, and 80 electrons when neutral
IUPAC standard atomic weight
Zinc group
What Mercury is used for
- Fluorescent lamps
- Electrical switches and relays
- Historically, thermometers and barometers
- Chlor-alkali chemical production
Atomic structure of Mercury
A neutral mercury atom has 80 protons and 80 electrons. Its most common isotope carries about 121 neutrons, which is where the mass number 201 comes from. Change the neutron count and you have a different isotope of mercury; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 18, 2. In orbital notation that is [Xe] 6s² 4f¹⁴ 5d¹⁰. As a d-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Mercury's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Mercury sits in the periodic table
The d-block. Multiple stable oxidation states give them coloured compounds, catalytic ability and the strength that makes them the working metals of industry.
- Directly above: Cadmium — same group, so similar chemistry with a smaller atom.
- Directly below: Copernicium — same group, one shell larger.
- One proton lighter: Gold.
- One proton heavier: Thallium.
Discovery and naming
Mercury has been known and used since antiquity, long before anyone could describe it as an element. Its name comes from The planet Mercury; symbol from Latin hydrargyrum, which is also why its symbol (Hg) does not match its English name.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Mercury?
The standard atomic weight of Mercury is 200.59 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Mercury have?
Mercury has 80 protons, because the atomic number is the proton count and that is what makes an atom Mercury at all. A neutral Mercury atom has the same number of electrons, 80. The neutron count varies by isotope; the most common one has about 121, since 201 − 80 = 121.
What is the electron configuration of Mercury?
The electron configuration of Mercury is [Xe] 6s² 4f¹⁴ 5d¹⁰. Its electrons are arranged 2, 8, 18, 32, 18, 2 across 6 shells.
Is Mercury a metal?
Yes. Mercury is classified as a transition metal, on the metallic side of the table.
What group and period is Mercury in?
Mercury is in group 12 (the zinc group), period 6, in the d-block. The group is its column and the period is its row.
What is the charge of Mercury?
Mercury most commonly forms a 2+ or 1+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound.
What is the melting point of Mercury?
Mercury melts at -38.83 °C and boils at 357 °C. That puts it in the short list of elements that are liquid at room temperature at everyday temperatures.
What is Mercury used for?
Fluorescent lamps, Electrical switches and relays, Historically, thermometers and barometers, Chlor-alkali chemical production. Mercury is the only metal that is liquid at room temperature, which made it the heart of thermometers and barometers for centuries.
Who discovered Mercury, and where does its name come from?
Mercury (Hg) has been known and used since antiquity, long before anyone could describe it as an element. The name comes from The planet Mercury; symbol from Latin hydrargyrum.