91Pa231.04
Protactinium
Actinide · element 91 · f-block (shown below the main table)
Quick facts
| Symbol | Pa |
|---|---|
| Atomic number | 91 |
| Relative atomic mass | 231.04 |
| Category | Actinide |
| Position | f-block (shown below the main table) |
| State at 20 °C | Solid |
| Melting point | 1,568 °C |
| Boiling point | — |
| Density | 15.37 g/cm³ |
| Electronegativity | 1.5 |
| Electron configuration | [Rn] 5f2 6d1 7s2 |
About Protactinium
Protactinium has the symbol Pa and atomic number 91, which means every protactinium atom has 91 protons in its nucleus and, in a neutral atom, 91 electrons. At room temperature it is a solid.
Actinides are the second row of the f-block. They are all radioactive, and only a few (like uranium and thorium) occur naturally in large amounts.
It melts at 1,568 °C.
Explore it
See where protactinium sits, and drag the temperature slider to watch it melt and boil, on the interactive periodic table. Practise with quizzes on OmniEx.