Transition metalElement 80 · d-block

Mercury (Hg)

Mercury (Hg) is a transition metal with atomic number 80 and a standard atomic weight of 200.59. At room temperature it is a liquid that melts at -39 °C and boils at 357 °C.

80HgMercury200.59

Atomic number

protons

Atomic weight

200.59

CIAAW 2024

Melting point

-39 °C

234.32 K

Boiling point

357 °C

629.77 K

Density

13.534 g/cm³

near room temperature

Electronegativity

Pauling scale

State at 25 °C

Liquid

Discovered

Antiquity

Mercury at a glance

Identity

Symbol	Hg
Atomic number (Z)	80
Atomic weight	200.59 ± 0.01 (CIAAW 2024)
Category	Transition metal
Group	12
Period	6
Block	d-block
CAS number	7439-97-6

Atomic properties

Electron configuration	[Xe] 4f¹⁴ 5d¹⁰ 6s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s²
Electrons per shell	2, 8, 18, 32, 18, 2
Oxidation states	+1, +2 Less common: -2
Electronegativity (Pauling)	2
First ionisation energy	10.438 eV (1,007.1 kJ/mol) 2nd: 18.757 eV · 3rd: 34.49 eV
Atomic radius (empirical)	150 pm
Covalent radius	133 pm
Van der Waals radius	223 pm

Physical properties

State at 25 °C	Liquid
Melting point	-38.83 °C · -37.9 °F · 234.32 K
Boiling point	356.6 °C · 673.9 °F · 629.77 K
Density	13.5336 g/cm³
Specific heat capacity	0.14 J/(g·K)
Thermal conductivity	8.3 W/(m·K)
Crystal structure	Rhombohedral

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	²⁰²Hg 29.74%, ²⁰⁰Hg 23.14%, ¹⁹⁹Hg 16.94%, ²⁰¹Hg 13.17%, ¹⁹⁸Hg 10.04%, ²⁰⁴Hg 6.82%
Stable isotopes	7
Known isotopes	47
Abundance in Earth's crust	0.085 mg/kg
Abundance in seawater	0.00003 mg/L

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Mercury electron configuration

Mercury has 80 electrons. Written in short form, its ground-state configuration is [Xe] 4f¹⁴ 5d¹⁰ 6s² — the electrons of the noble gas xenon, plus 4f¹⁴ 5d¹⁰ 6s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s².

4f↑↓↑↓↑↓↑↓↑↓↑↓↑↓

5d↑↓↑↓↑↓↑↓↑↓

6s↑↓

Discovery and name

Discovered

Antiquity — Known since antiquity (found in Egyptian tombs of c. 1500 BC).

Name

The planet/god Mercury; the symbol Hg is from Greek hydrargyrum, liquid silver.

Known for

The only metal liquid at room temperature. Once used in thermometers and barometers; now restricted because of its toxicity.

Isotopes of mercury

Naturally occurring mercury is a mix of 7 isotopes. Each has 80 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
²⁰²Hg	80	122	29.74%	stable
²⁰⁰Hg	80	120	23.14%	stable
¹⁹⁹Hg	80	119	16.94%	stable
²⁰¹Hg	80	121	13.17%	stable
¹⁹⁸Hg	80	118	10.04%	stable
²⁰⁴Hg	80	124	6.82%	stable
¹⁹⁶Hg	80	116	0.15%	stable

47 isotopes of mercury are known in our data set (half-lives as published in nuclear data tables).

Mercury compared with group 12

The other elements in group 12, from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Zinc	30	65.38	420 °C	907 °C	7.134 g/cm³	1.65
Cadmium	48	112.41	321 °C	767 °C	8.69 g/cm³	1.69
Mercury	80	200.59	-39 °C	357 °C	13.534 g/cm³	2
Copernicium	112	[285]	—	—	14 g/cm³ (pred.)	—

Frequently asked questions

6 answers

What is the atomic mass of mercury?

The standard atomic weight of mercury is 200.59 ± 0.01 (CIAAW 2024), so one mole weighs about 200.59 grams.

How many protons, neutrons and electrons does mercury have?

A neutral mercury atom has 80 protons and 80 electrons. Its most common isotope, mercury-202, has 122 neutrons.

What is the electron configuration of mercury?

[Xe] 4f¹⁴ 5d¹⁰ 6s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s²).

What are the melting and boiling points of mercury?

Mercury melts at -38.83 °C (-37.9 °F) and boils at 356.62 °C (673.9 °F).

Is mercury a metal?

Mercury is a metal. It is in group 12, period 6, and is a liquid at room temperature.

Who discovered mercury?

Mercury has been known since ancient times.