Plutonium (Pu): Bohr Model, Protons, Neutrons & Electrons
Plutonium is element number 94, an actinide in the f-block (the actinide row drawn below the table), period 7. Its atom has 94 protons, 150 neutrons and 94 electrons arranged in 7 shells: 2, 8, 18, 32, 24, 8, 2.
Protons, neutrons and electrons in plutonium
The atomic number of plutonium is 94, so every plutonium atom has 94 protons. A neutral atom has the same number of electrons, 94. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For plutonium-244, that is 244 − 94 = 150 neutrons. Every isotope of plutonium is radioactive; 244 is the mass number of its most stable one.
How to draw the Bohr model of plutonium
- Draw the nucleus and write 94 p⁺ and 150 n⁰ inside it.
- Draw the first shell and put 2 electrons on it (the first shell holds at most 2).
- Draw the second shell and put 8 electrons on it.
- Draw the third shell and put 18 electrons on it.
- Draw the fourth shell and put 32 electrons on it.
- Draw the fifth shell and put 24 electrons on it.
- Draw the sixth shell and put 8 electrons on it.
- Draw the seventh shell and put 2 electrons on it.
- Check: 2 + 8 + 18 + 32 + 24 + 8 + 2 = 94 electrons, the same as the number of protons.
From potassium onwards the shells don’t simply fill as 2, 8, 8: the fourth shell starts before the third is full, so the real arrangement above (2, 8, 18, 32, 24, 8, 2) is the one to draw.
Electron configuration
The electron configuration of plutonium is [Rn] 7s² 5f⁶. As an actinide it fills an inner f-subshell, and its common ion is Pu³⁺.
Key facts about plutonium
| Symbol | Pu |
|---|---|
| Atomic number | 94 |
| Relative atomic mass | [244] |
| Group · period · block | f-block · period 7 |
| Type | Actinide |
| State at 25 °C | solid |
| Electron shells | 2, 8, 18, 32, 24, 8, 2 |
| Electron configuration | [Rn] 7s² 5f⁶ |
| Valence electrons | varies (outer shell: 2) |
| Common ion | Pu³⁺ |
| Electronegativity (Pauling) | 1.28 |
| First ionisation energy | 6.03 eV (582 kJ/mol) |
| Atomic radius (empirical) | 175 pm |
Where plutonium sits on the periodic table
Frequently asked questions
How many protons, neutrons and electrons does plutonium have?
Plutonium has 94 protons and 94 electrons (atomic number 94). Its most common isotope, plutonium-244, has 244 − 94 = 150 neutrons.
What is the electron configuration of plutonium?
[Rn] 7s² 5f⁶. In shells that is 2, 8, 18, 32, 24, 8, 2.
How many valence electrons does plutonium have?
Plutonium is an actinide, so its valence electrons are spread over two shells; its outermost shell holds 2.
Where is plutonium on the periodic table?
In the f-block (the actinide row drawn below the table), period 7, in the f-block. It is an actinide.
