80HgMercury200.5923[Xe] 4f¹⁴ 5d¹⁰ 6s²
transition metal

Mercury

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.

Properties

At a glance

Atomic number
80
Atomic mass
200.5923 u
Phase
Liquid
Density
13.534 g/cm³
Melting point
234.321 K
Boiling point
629.88 K
First ionization energy
1,007.1 kJ/mol
Electronegativity
2
Electron affinity
-48 kJ/mol
Molar heat capacity
27.983 J/(mol·K)
Period
6
Appearance
silvery

Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.

Electronic structure

Mercury’s orbitals use a hydrogen-like approximation. Every orbital of each visible subshell is shown: in Shapes as the surface holding half its probability, with light and dark shades for opposite signs of the wavefunction; in Cloud as dots where its electrons are likely to be. Sizes are stepped by shell, like the Shell model.

Electrons by shell
Electron configuration

54 is the [Xe] core total across five shells.

Preparing the orbital view…

80 protons122 neutrons

Mercury-202: its most common form in nature, or its longest-lived if it has none. The nucleus is drawn far too big: it’s about 100,000 times smaller than the atom.

States of matter

Turn up the heat

298 KK stands for kelvin, the temperature scale used in science. It starts at absolute zero (0 K), the coldest temperature possible, so it has no negative numbers and no degree sign.

A step of 1 K is the same size as 1 °C, so the two scales are always 273.15 apart. Fahrenheit is different: its degrees are smaller and it starts elsewhere, so water freezes at 273.15 K, 0 °C and 32 °F.25 °C · 77 °FLiquid

At this temperature, mercury is a liquid.

At normal atmospheric pressure (1 atm). The temperature scale is logarithmic. The particle box is schematic: real samples hold vastly more atoms, and spacing and speeds are not to scale.

Ionization energy

Pull the electrons off

Hg

HgNeutral atom · no charge

A neutral mercury atom. Removing its first electron takes 1,007 kJ/mol.

Mercury’s outer shell holds 2 electrons. Electron 3 is the first from an inner shell: it sits closer to the nucleus with less shielding, so removing it takes 1.8× as much energy as the one before. Each dashed line on the chart marks another jump, into a shell even closer to the nucleus.

Shell 1Shell 2Shell 3Shell 4Shell 5Shell 6MeasuredEstimated or calculatedEnergy in kJ/molkJ/mol (kilojoules per mole) is the energy to remove that electron from every atom in a mole of them: about 602 sextillion (6.02 × 10²³) atoms. For a single atom, divide by 96.485 to get electronvolts (eV). Mercury’s first electron takes about 10 eV.
1,00010,000100,0001,000,00010,000,000Shell 5Shell 4Shell 3×1.8×1.1×1.7×2.2×415101520253035404550556065707580
Show the values as a table
ElectronShellEnergy (kJ/mol)× previousValue
161,007–Measured
261,8101.8Measured
353,3281.8Measured
454,6841.4Measured
555,9051.3Measured
657,3911.3Measured
758,9731.2Measured
8510,9901.2Calculated
9512,9291.2Calculated
10514,7621.1Calculated
11516,6921.1Calculated
12518,5931.1Estimated
13526,7171.4Estimated
14529,6211.1Calculated
15532,0331.1Calculated
16534,4451.1Calculated
17538,7871.1Calculated
18541,3921.1Calculated
19546,0241.1Calculated
20551,1371.1Calculated
21454,0321.1Calculated
22456,9261.1Calculated
23462,7151.1Calculated
24468,5051.1Calculated
25473,3291.1Calculated
26479,1181.1Calculated
27484,9071.1Calculated
28489,7311.1Calculated
29495,5201.1Calculated
304101,3101.1Calculated
314107,0991.1Calculated
324111,9231Calculated
334117,7121.1Calculated
344123,5011Calculated
354149,4561.2Calculated
364154,6661Calculated
374160,2621Calculated
384166,2441Calculated
394171,7441Calculated
404177,4371Calculated
414186,0241Calculated
424191,9091Calculated
434197,9881Calculated
444203,8741Calculated
454227,1261.1Calculated
464232,7231Calculated
474239,0911Calculated
484244,9761Calculated
494264,8521.1Calculated
504271,6061Calculated
514287,6231.1Calculated
524294,2711Estimated
533487,7331.7Calculated
543500,8551Calculated
553514,7491Calculated
563529,7041Calculated
573543,7911Calculated
583557,6851Calculated
593582,8681Calculated
603597,4371Calculated
613613,2611Calculated
623627,9271Calculated
633668,9331.1Calculated
643681,7651Calculated
653695,7561Calculated
663709,1671Calculated
673772,8481.1Calculated
683787,3201Calculated
693817,2311Calculated
703831,7041Calculated
7121,789,8032.2Calculated
7221,824,5381Calculated
7321,863,1321Calculated
7421,898,8311Calculated
7522,134,2561.1Calculated
7622,178,6391Calculated
7722,235,5651Calculated
7822,271,6601Calculated
7919,081,6534Calculated
8019,252,7691Calculated

Successive ionization energies of gas-phase atoms and ions from the NIST Atomic Spectra Database. Solid bars are measured; hatched bars were estimated from nearby measurements or calculated from quantum theory, as is usual for highly charged ions. Electrons are taken from the outermost shell first, a simplification: electrons in different subshells of the same shell also differ in energy. On the log scale each gridline is 10 times the one below.

Emission spectrum

A fingerprint made of light

Hgbluish white

Mercury’s violet, blue and green lines, and its strong ultraviolet ones, light fluorescent lamps: a coating inside the tube turns the ultraviolet into visible light.

Heated or electrified, mercury gives off light only at the exact wavelengths below. Each one comes from an electron falling between two energy levels, so the pattern is unique to the element, like a fingerprint.

Wavelength in nanometresA nanometre (nm) is a billionth of a metre. Our eyes see light from about 380 nm (violet) to 750 nm (red); a human hair is about 80,000 nm wide.
Mercury spectral lines

Click a line to see where it comes from.

404.7 nmviolet

An electron falls from the 7s level down to the 6p level. It loses 3.06 eV of energyAn electronvolt (eV) is a tiny unit of energy used for atoms: the energy one electron gains crossing 1 volt. A particle of visible light carries between about 1.7 eV (red) and 3.3 eV (violet). and gives it off as one particle of violet light. Bigger drops give bluer light.

Energy7s · 7.73 eV6p · 4.67 eV0 eV · ground

The strongest visible lines of neutral mercury from the NIST Atomic Spectra Database. Line brightness follows NIST’s relative intensities, which only compare lines of the same element. Colours are approximate, and lamp colours are as they look to the eye.

Why is it liquid?

Why is mercury liquid? Blame Einstein

Mercury is the only metal that’s liquid at room temperature. The reason is surprising: Einstein’s theory of relativity. Its 80 protons pull its electrons so hard that the innermost ones race at over half the speed of light, and that changes how the whole atom behaves.

+80

The real mercury atom

Innermost electrons
Race at about 58% of the speed of light (orange)
At that speed
They act about 23% heavier, so they huddle about 19% closer
Outer electrons
Pulled in too, held tightly, and hard to share (blue)
Melts at
−39 °C (measured)

Metal atoms stick together by sharing their outer electrons. Mercury keeps its two held so tightly that its atoms barely stick, so a little warmth lets them slide apart: it melts at −39 °C.

E = mc², at speed

Einstein’s E = mc² says that even a resting electron carries energy: 511 keV. The full version, E = γmc², adds a factor γ that grows with speed. The more protons an atom has, the faster its innermost electrons race, and the more γ matters. Slide through the elements to see it.

Speed of the innermost electrons58% of light speed
Energy of each oneA kilo-electronvolt: a tiny unit of energy used for atoms and particles. 1 keV is the energy an electron gains crossing 1,000 volts.629 keV, 23% more than at rest
Pulled in closer by19%

E = mc² at rest = 511 keV

γ = 1 ÷ √(1 − v²/c²) = 1 ÷ √(1 − 0.584²) = 1.232

E = γmc² = 1.232 × 511 keV = 629 keV

1230%25%50%75%c

γ barely moves at everyday speeds, even at the speed of a rocket. It only takes off as you get close to the speed of light, which is why only heavy atoms, with lots of protons pulling hard, feel it.

Try it at different temperatures

20 °C, relativity onLiquid

The odd one out in its family

Zinc, cadmium and mercury sit in the same column of the table. Going down a column, atoms get bigger and usually let go of their outer electrons more easily. Mercury breaks the pattern: it grips them hardest of all, and melts hundreds of degrees lower.

  • ZincMelts at 420 °CGrip on its outer electrons: 906.4 kJ/mol
  • CadmiumMelts at 321 °CGrip on its outer electrons: 867.8 kJ/mol
  • MercuryMelts at −39 °CGrip on its outer electrons: 1,007.1 kJ/mol

The electron speed (about Z/137 of light speed for the innermost electrons), γ and size change are rough estimates from a simple model of the atom; the electron’s rest energy, 511 keV, is the measured (CODATA) value. The effect on the melting point comes from computer simulations by Calvo, Pahl, Wormit and Schwerdtfeger (Angewandte Chemie, 2013). “Grip” is the first ionization energy, the energy needed to pull off one outer electron (NIST).

Compared with other elements

How does it compare?

MercuryGroup 12Other elements

Density

13.5 g/cm³14th highest of 99

Hg

Melting point

234 K11th lowest of 96

Hg

Boiling point

630 K16th lowest of 97

Hg

Electronegativity

231st highest of 96

Hg

First ionization energy

1,007 kJ/mol16th highest of 99

Hg

Elements 1–99 from the reference data; heavier elements are left out because only a few atoms have ever been made, so their bulk properties are predictions. First ionization energies come from NIST. Density uses a logarithmic scale, because gases are around a thousand times less dense than solids; gas densities are at 0 °C and 1 atm. Melting and boiling points are at normal pressure. Everyday temperatures and light sources in the pictures are approximate. Hover over a dot to see the element, or click it to compare.

Keep exploring

Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.