Samarium (Sm)
Samarium is element 62, a lanthanide in the lanthanide series (period 6). A neutral atom has 62 protons, 88 neutrons and 62 electrons, 2 of them valence electrons.
Lanthanide- Atomic number
- 62
- Atomic mass
- 150.4 u
- Valence electrons
- 2*
- Protons · neutrons
- 62 · 88
- Electrons per shell
- 2, 8, 18, 24, 8, 2
- At room temperature
- solid
Bohr model of samarium
The Bohr model draws samarium as a nucleus of 62 protons and 88 neutrons, with its 62 electrons on 6 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 24 in shell 4, 8 in shell 5, 2 in shell 6. Press Build the atom to watch the shells fill from the inside out. The outer ring (the P 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 samarium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁶
Short form (noble gas notation): [Xe] 6s² 4f⁶. The [Xe] stands for the electrons of xenon, the noble gas before it.
How many valence electrons does samarium have?
Samarium has 2 valence electrons.
Samarium is a lanthanide, so its valence electrons are less clear-cut than for main-group elements. It has 2 electrons in its outermost shell (shell 6), and electrons in its inner f and d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 62 | equal to the atomic number |
|---|---|---|
| Electrons | 62 | equal to the protons in a neutral atom |
| Neutrons | 88 | mass number 150 − 62 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.
Samarium properties
| Symbol | Sm |
|---|---|
| Category | Lanthanide |
| Group · period · block | — · 6 · f |
| Atomic mass | 150.4 u |
| State at 25 °C | solid |
| Melting point | 1,347 K (1,070 °C, 1,960 °F) |
| Boiling point | 2,067 K (1,790 °C, 3,260 °F) |
| Density | 7.52 g/cm³ |
| Electronegativity (Pauling) | 1.17 |
| Atomic radius | 229 pm |
| First ionization energy | 5.644 eV |
| Electron affinity | — |
| Oxidation states | +3, +2 |
| Common ion charge | +3, +2 |
| Discovered | 1879 by Lecoq de Boisbaudran |
Where samarium sits on the periodic table
Lanthanides: Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Europium, Gadolinium, Terbium.
Questions about samarium
How many valence electrons does samarium have?
Samarium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does samarium have?
A neutral samarium atom has 62 protons and 62 electrons. Its most common form has about 88 neutrons (mass number 150 − 62 protons).
What is the electron configuration of samarium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁶, written in short form as [Xe] 6s² 4f⁶.
What does the Bohr model of samarium look like?
A nucleus of 62 protons and 88 neutrons, circled by 6 electron shells holding 2, 8, 18, 24, 8, 2 electrons.
What is the atomic number of samarium?
62. The atomic number is the number of protons in the nucleus, and it is what makes an atom samarium.