Uranium (U)
Uranium is element 92, an actinide in the actinide series (period 7). A neutral atom has 92 protons, 146 neutrons and 92 electrons, 2 of them valence electrons.
Actinide- Atomic number
- 92
- Atomic mass
- 238.03 u
- Valence electrons
- 2*
- Protons · neutrons
- 92 · 146
- Electrons per shell
- 2, 8, 18, 32, 21, 9, 2
- At room temperature
- solid
Bohr model of uranium
The Bohr model draws uranium as a nucleus of 92 protons and 146 neutrons, with its 92 electrons on 7 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 21 in shell 5, 9 in shell 6, 2 in shell 7. Press Build the atom to watch the shells fill from the inside out. The outer ring (the Q shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of uranium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f³ 6d¹
Short form (noble gas notation): [Rn] 7s² 5f³ 6d¹. The [Rn] stands for the electrons of radon, the noble gas before it.
Uranium breaks the usual filling order. The Aufbau rule predicts 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁴, but experiments show the configuration above. The energy levels of the subshells are so close here that a different arrangement wins.
How many valence electrons does uranium have?
Uranium has 2 valence electrons.
Uranium is a actinide, so its valence electrons are less clear-cut than for main-group elements. It has 2 electrons in its outermost shell (shell 7), and electrons in its inner f and d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 92 | equal to the atomic number |
|---|---|---|
| Electrons | 92 | equal to the protons in a neutral atom |
| Neutrons | 146 | mass number 238 − 92 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Uranium properties
| Symbol | U |
|---|---|
| Category | Actinide |
| Group · period · block | — · 7 · f |
| Atomic mass | 238.03 u |
| State at 25 °C | solid |
| Melting point | 1,408 K (1,130 °C, 2,070 °F) |
| Boiling point | 4,404 K (4,130 °C, 7,470 °F) |
| Density | 18.95 g/cm³ |
| Electronegativity (Pauling) | 1.38 |
| Atomic radius | 240 pm |
| First ionization energy | 6.194 eV |
| Electron affinity | — |
| Oxidation states | +6, +5, +4, +3 |
| Common ion charge | +6, +5 |
| Discovered | 1789 by Martin Heinrich Klaproth |
Where uranium sits on the periodic table
Actinides: Actinium, Thorium, Protactinium, Neptunium, Plutonium, Americium, Curium, Berkelium.
Questions about uranium
How many valence electrons does uranium have?
Uranium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does uranium have?
A neutral uranium atom has 92 protons and 92 electrons. Its most common form has about 146 neutrons (mass number 238 − 92 protons).
What is the electron configuration of uranium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f³ 6d¹, written in short form as [Rn] 7s² 5f³ 6d¹.
What does the Bohr model of uranium look like?
A nucleus of 92 protons and 146 neutrons, circled by 7 electron shells holding 2, 8, 18, 32, 21, 9, 2 electrons.
What is the atomic number of uranium?
92. The atomic number is the number of protons in the nucleus, and it is what makes an atom uranium.