hafnium (Hf): Bohr Model, Protons, Neutrons & Electrons
hafnium is element number 72, a transition metal in group 4, period 6. Its atom has 72 protons, 108 neutrons and 72 electrons arranged in 6 shells: 2, 8, 18, 32, 10, 2.
- 72 protons
- 108 neutrons
- 72 electrons
Protons, neutrons and electrons in hafnium
Le atomic number of hafnium is 72, so every hafnium atom has 72 protons. A neutral atom has the same number of electrons, 72. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For hafnium-180, that is 180 − 72 = 108 neutrons. Hafnium has 6 stable isotopes, with 102, 104, 105, 106, 107, 108 neutrons.
How to draw the Bohr model of hafnium
- Draw the nucleus and write 72 p⁺ et 108 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 10 electrons on it.
- Draw the sixth shell and put 2 electrons on it.
- Check: 2 + 8 + 18 + 32 + 10 + 2 = 72 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, 10, 2) is the one to draw.
Electron configuration
The electron configuration of hafnium is [Xe] 6s² 4f¹⁴ 5d². As a transition metal it fills an inner d-subshell, and its common ion is Hf⁴⁺.
Key facts about hafnium
| Symbol | Hf |
|---|---|
| Atomic number | 72 |
| Relative atomic mass | 178.49 |
| Group · period · block | group 4 · period 6 · d-block |
| Type | Métal de transition |
| State at 25 °C | solid |
| Couches électroniques | 2, 8, 18, 32, 10, 2 |
| Electron configuration | [Xe] 6s² 4f¹⁴ 5d² |
| Électrons de valence | varies (outer shell: 2) |
| Common ion | Hf⁴⁺ |
| Electronegativity (Pauling) | 1.30 |
| First ionisation energy | 6.83 eV (659 kJ/mol) |
| Atomic radius (empirical) | 155 pm |
Où hafnium sits on the periodic table
Foire aux questions
How many protons, neutrons and electrons does hafnium have?
Hafnium has 72 protons and 72 electrons (atomic number 72). Its most common isotope, hafnium-180, has 180 − 72 = 108 neutrons.
What is the electron configuration of hafnium?
[Xe] 6s² 4f¹⁴ 5d². In shells that is 2, 8, 18, 32, 10, 2.
How many valence electrons does hafnium have?
Hafnium is a transition metal, so its valence electrons are spread over two shells; its outermost shell holds 2.
Where is hafnium on the periodic table?
In group 4, period 6, in the d-block. It is a transition metal.
