Chemical element · reference page

88Ra

Radium

Radium is element 88 (Ra), located in period 7, group 2 and the s block. At room temperature its reference phase is solid. Its electron configuration is [Rn] 7s2.

Atomic number88

Standard atomic weightNo standard atomic weight

Group2

Period7

Blocks

Electron configuration[Rn] 7s2

Electronic structure

What controls its chemistry

The outer configuration ends in s². Removing two valence electrons produces a +2 ion, which is the characteristic ionic state of the alkaline-earth metals.

Compared with group 1 metals, the two-electron outer shell changes ionisation energies, bonding and reactivity. Their compounds commonly occur as oxides, carbonates, sulfates or halides rather than as free metals in nature.

Chemical forms

Compounds, ions and materials

The +2 oxidation state dominates. Oxides, hydroxides, halides, carbonates and sulfates are common families of radium compounds, although their solubility and thermal stability vary systematically down group 2.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 5.0g/cm³. The melting point is 1 233 K (959.9 °C). The boiling point is 1 773K (1 737 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where radium is found and used

In practice, radium is encountered in scientific research, history and medicine history.

In practice

Examples of real uses

Scientific research

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

History

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

Medicine history

Radium was historically used in medicine before its risks and limitations were fully understood; modern practice may use safer alternatives.

Periodic position

What its neighbours tell us

Radium is in period 7 and group 2. In the neighbourhood shown here, francium is immediately to its left in the same period; barium is directly above 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

Classificationalkaline earth metal

Phase at room temperatureSolid

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

Density5.0g/cm³

Melting point1 233 K (959.9 °C)

Boiling point1 773K (1 737 °C)

Pauling electronegativity0.9

First ionisation energy509.3 kJ/mol

Electron affinity9.6485 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 radium 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

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

Radium 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

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