Copernicium (Cn)
Element 112 · Transition metal · atomic mass [285] u · group 12, period 7
Electron shells: 2, 8, 18, 32, 32, 18, 2
Copernicium sits below mercury and relativistic effects may make it even less metallic — some predictions have it as a gas at room temperature. Only a few dozen atoms have ever been made.
Copernicium might be a gas at room temperature — a metal so relativistically odd it stops behaving like one.
- Atomic number
- 112
- Atomic mass
- [285] u
- Electron configuration
- [Rn] 7s² 5f¹⁴ 6d¹⁰
- Group · period · block
- 12 · 7 · d
- Oxidation states
- 0, +1, +2
- Electronegativity
- Not measured
- Melting point
- —
- Boiling point
- —
- Density
- Not measured
- State at 20 °C
- Unknown
- Appearance
- Unknown; possibly a gas
- Discovered
- Sigurd Hofmann and colleagues, 1996
112 protons, and 112 electrons when neutral
Mass number of the longest-lived isotope — no standard atomic weight exists
Predicted, not measured
Zinc group
What Copernicium is used for
- Scientific research only
Atomic structure of Copernicium
A neutral copernicium atom has 112 protons and 112 electrons. Its most common isotope carries about 173 neutrons, which is where the mass number 285 comes from. Change the neutron count and you have a different isotope of copernicium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 32, 18, 2. In orbital notation that is [Rn] 7s² 5f¹⁴ 6d¹⁰. 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 Copernicium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Copernicium 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: Mercury — same group, so similar chemistry with a smaller atom.
- One proton lighter: Roentgenium.
- One proton heavier: Nihonium.
Discovery and naming
Copernicium was discovered by Sigurd Hofmann and colleagues in 1996. Its name comes from Nicolaus Copernicus, which is also why its symbol (Cn) does not match its English name.
Every isotope of copernicium is radioactive, so it has no standard atomic weight. Periodic tables show the mass number of its longest-lived isotope in square brackets instead.
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 Copernicium?
Copernicium has no stable isotope, so it has no standard atomic weight. Periodic tables instead show 285 in square brackets — the mass number of its longest-lived isotope.
How many protons, neutrons and electrons does Copernicium have?
Copernicium has 112 protons, because the atomic number is the proton count and that is what makes an atom Copernicium at all. A neutral Copernicium atom has the same number of electrons, 112. The neutron count varies by isotope; the most common one has about 173, since 285 − 112 = 173.
What is the electron configuration of Copernicium?
The electron configuration of Copernicium is [Rn] 7s² 5f¹⁴ 6d¹⁰, though for an element this heavy the configuration is predicted from theory rather than measured. Its electrons are arranged 2, 8, 18, 32, 32, 18, 2 across 7 shells.
Is Copernicium a metal?
Yes. Copernicium is classified as a transition metal, on the metallic side of the table.
What group and period is Copernicium in?
Copernicium is in group 12 (the zinc group), period 7, in the d-block. The group is its column and the period is its row.
What is Copernicium used for?
Scientific research only. Copernicium sits below mercury and relativistic effects may make it even less metallic — some predictions have it as a gas at room temperature.
Who discovered Copernicium, and where does its name come from?
Copernicium (Cn) was discovered by Sigurd Hofmann and colleagues in 1996. The name comes from Nicolaus Copernicus.
Is Copernicium radioactive?
Yes. Every isotope of Copernicium is radioactive — it has no stable form at all, which is why the periodic table shows its mass in square brackets rather than as a standard atomic weight.