Samarium (Sm): Bohr Model, Protons, Neutrons & Electrons
Samarium is element number 62, a lanthanide in the f-block (the lanthanide row drawn below the table), period 6. Its atom has 62 protons, 90 neutrons and 62 electrons arranged in 6 shells: 2, 8, 18, 24, 8, 2.
Protons, neutrons and electrons in samarium
The atomic number of samarium is 62, so every samarium atom has 62 protons. A neutral atom has the same number of electrons, 62. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For samarium-152, that is 152 − 62 = 90 neutrons. Samarium has 7 stable isotopes, with 82, 85, 86, 87, 88, 90, 92 neutrons.
How to draw the Bohr model of samarium
- Draw the nucleus and write 62 p⁺ and 90 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 24 electrons on it.
- Draw the fifth shell and put 8 electrons on it.
- Draw the sixth shell and put 2 electrons on it.
- Check: 2 + 8 + 18 + 24 + 8 + 2 = 62 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, 24, 8, 2) is the one to draw.
Electron configuration
The electron configuration of samarium is [Xe] 6s² 4f⁶. As a lanthanide it fills an inner f-subshell, and its common ion is Sm³⁺.
Key facts about samarium
| Symbol | Sm |
|---|---|
| Atomic number | 62 |
| Relative atomic mass | 150.36 |
| Group · period · block | f-block · period 6 |
| Type | Lanthanide |
| State at 25 °C | solid |
| Electron shells | 2, 8, 18, 24, 8, 2 |
| Electron configuration | [Xe] 6s² 4f⁶ |
| Valence electrons | varies (outer shell: 2) |
| Common ion | Sm³⁺ |
| Electronegativity (Pauling) | 1.17 |
| First ionisation energy | 5.64 eV (544 kJ/mol) |
| Atomic radius (empirical) | 185 pm |
Where samarium sits on the periodic table
Frequently asked questions
How many protons, neutrons and electrons does samarium have?
Samarium has 62 protons and 62 electrons (atomic number 62). Its most common isotope, samarium-152, has 152 − 62 = 90 neutrons.
What is the electron configuration of samarium?
[Xe] 6s² 4f⁶. In shells that is 2, 8, 18, 24, 8, 2.
How many valence electrons does samarium have?
Samarium is a lanthanide, so its valence electrons are spread over two shells; its outermost shell holds 2.
Where is samarium on the periodic table?
In the f-block (the lanthanide row drawn below the table), period 6, in the f-block. It is a lanthanide.
