Chemical element · reference page

80Hg

Mercury

Mercury is element 80 (Hg), located in period 6, group 12 and the d block. At room temperature its reference phase is liquid. Its electron configuration is [Xe] 4f14 5d10 6s2.

Atomic number80

Standard atomic weight200.592(3)

Group12

Period6

Blockd

Electron configuration[Xe] 4f14 5d10 6s2

Electronic structure

What controls its chemistry

The d subshell participates in the chemistry of mercury. Transition metals can use electrons of similar energies in bonding, which is why variable oxidation states, coordination compounds and catalytic behaviour are common across the d block.

Its electron configuration, [Xe] 4f14 5d10 6s2, should be read together with the oxidation state of the compound: removing electrons changes which d orbitals are occupied and can alter colour, magnetism, bonding and reactivity.

Chemical forms

Compounds, ions and materials

For mercury, important chemical forms include metals and alloys, oxides, halides and coordination compounds. Variable oxidation states are common because s and d electrons have similar energies, and ligands around the metal ion can strongly alter colour, magnetism and reactivity.

Physical behaviour

State and phase changes

The reference phase at room temperature is liquid. The listed density is 13.53 g/cm³. The melting point is 234.3 K (-38.8 °C). The boiling point is 629.9 K (356.7 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where mercury is found and used

In practice, mercury is encountered in measurement, lamps and chemical synthesis.

In practice

Examples of real uses

Measurement

Mercury is used in instruments because a physical property such as expansion, electrical response or atomic transition can be measured accurately.

Lamps

Mercury is used in lamp gases, electrodes, phosphors or specialised light-producing components.

Chemical synthesis

Mercury is used as an element, reagent, catalyst component or precursor in the manufacture of other chemicals.

Periodic position

What its neighbours tell us

Mercury is in period 6 and group 12. In the neighbourhood shown here, it lies between gold and thallium in the same period; cadmium is above it and copernicium below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.

Reference data

Physical and atomic properties

Classificationtransition metal

Phase at room temperatureLiquid

Electron shells2 · 8 · 18 · 32 · 18 · 2

Density13.53 g/cm³

Melting point234.3 K (-38.8 °C)

Boiling point629.9 K (356.7 °C)

Pauling electronegativity2

First ionisation energy1 007 kJ/mol

Electron affinity—

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

Mercury was known before 2000 BCE, with no single discoverer identified in this record. Its early use predates modern chemistry, so use of the material, chemical identification and the later atomic-number definition are separate stages.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is 200.592(3). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Mercury has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

Mercury exposure depends strongly on chemical form. Vapour and some organic mercury compounds are particularly hazardous.