Promethium has no stable isotopes.
Uses and research
It is a radioactive lanthanide used mainly in specialized applications and research.
Similar elements with different applications
The lanthanides are shown in a separate row below the main table. Their chemical similarities can make separation difficult. Differences in optical and magnetic behavior, however, lead to different uses. Comparing neighboring elements helps show why a family of similar elements is useful in many distinct materials.
What the atomic number tells us
Promethium has atomic number 61. This is the number of protons in its nucleus. A neutral atom also has 61 electrons. Losing or gaining electrons makes an ion; it does not change the element unless the proton count changes.
The model's rings help count electrons by shell. They are not actual circular paths. A model of one atom and the properties of a whole material are different levels of description.
Temperature and state
25°C: Solid
Illustrative particle motion: sizes, distances and speeds are not to scale. Particles represent atoms or molecules.
← CoolHeat →
Melting point 1,041.85°C / Boiling point 2,999.85°C
Pure element at 1 atmosphere. Image conditions are explained in captions. Pictures do not change with temperature.