Chemical element · Atomic number 88
Radium
Radium in the periodic table: atomic number 88, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Alkaline earth metal
solid
[226.02541] u
Generated illustrationGenerated illustration, Quanta Study. Not a photograph of a sample.
Generated illustration of Radium; the image does not show a sample of the element.
Highly radioactive element; no freely licensed photograph of a sample is available.
Code-native illustration with the Quanta Study mark inside the image; not a photograph, no AI model involved.
Atomic classification
Shell occupancy
Radium in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 8 electrons
- M · n=3
- 18 electrons
- N · n=4
- 32 electrons
- O · n=5
- 18 electrons
- P · n=6
- 8 electrons
- Q · n=7
- 2 electrons
- Electron configuration
- [Rn]7s2
- Electrons per shell
- 2 · 8 · 18 · 32 · 18 · 8 · 2
- Group
- 2
- Period
- 7
- Block
- S
- Element category
- Alkaline earth metal
Physical and chemical properties
- Atomic mass
- [226.02541] u
- Standard state
- solid
- Density
- 5 g/cm³
- Melting point
- 973 K
- Boiling point
- 1,413 K
- Electronegativity
- 0.9 (Pauling)
- First ionisation energy
- 5.279 eV
- Oxidation states
- +2
- Discovery
- 1898
Safety and periodic classification
Safety
Safe handling cannot be inferred from Radium's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Radium is in period 7, group 2 and the S block. Its direct neighbours by atomic number are Francium and Actinium. The recorded Pauling electronegativity is 0.9. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.
Where Radium sits among the 118 elements
The table compares the reported values for Radium with every other element that carries the same value in the snapshot. A rank is not a judgement, it is orientation: it says how unusual this value is across the periodic table.
| Value | Radium | Position in the data set |
|---|---|---|
| Melting point | 973 K | Rank 64 of 103 elements with a reported value. Highest: Carbon. |
| Boiling point | 1,413 K | Rank 66 of 93 elements with a reported value. Highest: Rhenium. |
| Density | 5 g/cm³ | Rank 63 of 96 elements with a reported value. Highest: Osmium. |
| Electronegativity (Pauling) | 0.9 | Rank 90 of 95 elements with a reported value. Highest: Fluorine. |
| Ionisation energy | 5.279 eV | Rank 95 of 102 elements with a reported value. Highest: Helium. |
All values and ranks come from the PubChem Periodic Table snapshot, retrieved on 2026-07-15. Elements without a reported value are excluded, so the population differs per row.
The neighbours of Radium in the periodic table
- Place in the table
- Group 2, period 7, S block. Classified as alkaline earth metal, solid at standard conditions.
- Direct neighbours
- Atomic number 88. Preceded by Francium, followed by Actinium.
- Same group
- Same number of outer electrons, and therefore similar reactivity to Beryllium, Magnesium, Calcium, Strontium, Barium.
- Discovery
- Recorded in the snapshot as: 1898. Who, where and under what circumstances is not part of that record, so this page carries the sourced year and no discovery narrative.
- Oxidation states
- +2. They follow from the electron configuration [Rn]7s2 and indicate which compounds to expect.
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