Chemical element · reference page

84Po

Polonium

Polonium is element 84 (Po), located in period 6, group 16 and the p block. At room temperature its reference phase is solid. Its electron configuration is [Xe] 4f14 5d10 6s2 6p4.

Atomic number84

Standard atomic weightNo standard atomic weight

Group16

Period6

Blockp

Electron configuration[Xe] 4f14 5d10 6s2 6p4

Electronic structure

What controls its chemistry

Group 16 atoms have six valence electrons. Bonding often involves gaining or sharing two electrons, while the heavier members can access a wider range of oxidation states.

For polonium, this outer-shell structure helps explain the importance of oxides, sulfides, oxoanions and covalent compounds across the chalcogen family.

Chemical forms

Compounds, ions and materials

Hydrides, oxides, sulfides or selenides, halides and oxoanions are important across group 16. The −2 oxidation state is common for the lighter chalcogens, while positive oxidation states become increasingly accessible in heavier compounds.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 9.196 g/cm³. The melting point is 527 K (253.9 °C). The boiling point is 1 235 K (961.9 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where polonium is found and used

In practice, polonium is encountered in scientific research, nuclear heat and history.

In practice

Examples of real uses

Scientific research

Polonium is produced, isolated or measured mainly to test atomic, nuclear and periodic trends rather than for bulk commercial use.

Nuclear heat

Radioactive decay of polonium releases heat that can be used in specialised scientific or power systems.

History

Polonium is important in the history of chemistry, medicine or technology even where modern use is limited.

Periodic position

What its neighbours tell us

Polonium is in period 6 and group 16. In the neighbourhood shown here, it lies between bismuth and astatine in the same period; tellurium is above it and livermorium 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

Classificationpost-transition metal

Phase at room temperatureSolid

Electron shells2 · 8 · 18 · 32 · 18 · 6

Density9.196 g/cm³

Melting point527 K (253.9 °C)

Boiling point1 235 K (961.9 °C)

Pauling electronegativity2

First ionisation energy812.2kJ/mol

Electron affinity136 kJ/mol

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

History

Discovery and identification

The discovery of polonium is associated with Pierre Curie. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

Polonium has no standard atomic weight. There is no characteristic terrestrial isotopic mixture from which a stable abundance-weighted average can be assigned.

Polonium has no stable isotope. Its isotopes are radioactive, and their half-lives and decay modes become important whenever the element is measured, handled or used.

Safety

Handling and exposure

Polonium is radioactive. Work with it requires radiological controls appropriate to the isotope, activity, radiation type and chemical form.