A neutron collides with a U-235 atom. U-236 forms briefly before it undergoes nuclear fission; this yields new atoms plus energy plus more neutrons. These newly released neutrons can cause more U-235 to split. If U-235 atoms are present in high enough concentrations, a nuclear chain reaction results. Image by Fastfission
Data Zone
| Classification: | Uranium is an actinide metal |
| Color: | silvery-white |
| Atomic weight: | 238.0289, no stable isotopes |
| State: | solid |
| Melting point: | 1135 oC, 1408 K |
| Boiling point: | 4130 oC, 4403 K |
| Electrons: | 92 |
| Protons: | 92 |
| Neutrons in most abundant isotope: | 146 |
| Electron shells: | 2,8,18,32,21,9,2 |
| Electron configuration: | [Rn] 5f3 6d1 7s2 |
| Density @ 20oC: | 18.9 g/cm3 |
| Atomic volume: | 12.59 cm3/mol |
| Structure: | orthorhombic |
| Hardness: | 6.0 mohs |
| Specific heat capacity | 0.12 J g-1 K-1 |
| Heat of fusion | 8.520 kJ mol-1 |
| Heat of atomization | 482 kJ mol-1 |
| Heat of vaporization | 422.58 kJ mol-1 |
| 1st ionization energy | 597.6 kJ mol-1 |
| 2nd ionization energy | 1420 kJ mol-1 |
| 3rd ionization energy | – |
| Electron affinity | – |
| Minimum oxidation number | 0 |
| Min. common oxidation no. | 0 |
| Maximum oxidation number | 6 |
| Max. common oxidation no. | 6 |
| Electronegativity (Pauling Scale) | – |
| Polarizability volume | 27.4 Å3 |
| Reaction with air | mild, ⇒ U3O8 |
| Reaction with 15 M HNO3 | passivated |
| Reaction with 6 M HCl | mild, ⇒ H2 |
| Reaction with 6 M NaOH | none |
| Oxide(s) | UO, UO2, UO3 , U2O5, U3O8 |
| Hydride(s) | UH3 |
| Chloride(s) | UCl, UCl3, UCl4, UCl5, UCl6 |
| Atomic radius | 175 pm |
| Ionic radius (1+ ion) | – |
| Ionic radius (2+ ion) | – |
| Ionic radius (3+ ion) | 116.5 pm |
| Ionic radius (1- ion) | – |
| Ionic radius (2- ion) | – |
| Ionic radius (3- ion) | – |
| Thermal conductivity | 27.5 W m-1 K-1 |
| Electrical conductivity | 3.6 x 10-6 S m-1 |
| Freezing/Melting point: | 1135 oC, 1408 K |
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