Unknown propertiesElement 112 · d-block

Copernicium (Cn)

Copernicium (Cn), element 112, is a synthetic superheavy element whose chemical properties have not been measured; its most stable known isotope has mass number 285. Only a few atoms have ever been made, so its bulk properties are predictions.

112CnCopernicium[285]

Atomic number

112

protons

Atomic weight

[285]

most stable isotope

Melting point

—

Boiling point

—

Density

14 g/cm³

predicted

Electronegativity

—

Pauling scale

State at 25 °C

Unknown

Discovered

1996

Germany (Darmstadt)

Copernicium at a glance

Identity

Symbol	Cn
Atomic number (Z)	112
Atomic weight	[285] mass number of the most stable isotope
Category	Unknown properties
Group	12
Period	7
Block	d-block
CAS number	54084-26-3

Atomic properties

Electron configuration	[Rn] 5f¹⁴ 6d¹⁰ 7s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d¹⁰ 7s²
Electrons per shell	2, 8, 18, 32, 32, 18, 2
Covalent radius	122 pm

Physical properties

State at 25 °C	Unknown
Density	14 g/cm³ (predicted)

Isotopes & abundance

Natural occurrence	Synthetic
Radioactive	Yes
Most stable isotope	²⁸⁵Cn — half-life 30 s
Known isotopes	13

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

Copernicium electron configuration

Copernicium has 112 electrons. Written in short form, its ground-state configuration is [Rn] 5f¹⁴ 6d¹⁰ 7s² — the electrons of the noble gas radon, plus 5f¹⁴ 6d¹⁰ 7s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d¹⁰ 7s².

5f↑↓↑↓↑↓↑↓↑↓↑↓↑↓

6d↑↓↑↓↑↓↑↓↑↓

7s↑↓

Discovery and name

Discovered

1996 — Sigurd Hofmann and co-workers (GSI) · Germany (Darmstadt).

Name

Nicolaus Copernicus.

Known for

Experiments suggest it is volatile and may be a liquid or gas at room temperature, owing to relativistic effects.

Isotopes of copernicium

Copernicium has no stable isotopes and does not occur naturally in significant amounts. Its longest-lived known isotope is:

Isotope	Protons	Neutrons	Half-life
²⁸⁵Cn	112	173	30 s

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

Copernicium 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

4 answers

What is the atomic mass of copernicium?

Copernicium has no stable isotopes, so it has no standard atomic weight. Periodic tables show [285], the mass number of its most stable known isotope.

How many protons, neutrons and electrons does copernicium have?

A neutral copernicium atom has 112 protons and 112 electrons. Its most stable isotope, copernicium-285, has 173 neutrons.

What is the electron configuration of copernicium?

[Rn] 5f¹⁴ 6d¹⁰ 7s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d¹⁰ 7s²).

Who discovered copernicium?

1996 — Sigurd Hofmann and co-workers (GSI) (Germany (Darmstadt)).