Neodymium vs Samarium
Both are lanthanides, so they share the same broad chemistry.
The differences in plain English
- They sit in the same column, group 3, so they have the same number of outer electrons and react in similar ways; the heavier one, Samarium, is usually the more reactive of the two if they are metals, and the less reactive if they are non-metals.
- Both are solids at room temperature.
- Samarium is denser, only slightly more than Neodymium (7.52 against 7.01 g/cm³).
- Samarium melts at 1072 °C, Neodymium at 1024 °C.
- An atom of Samarium is only slightly heavier than an atom of Neodymium (150.36 u against 144.24 u).
- Samarium pulls electrons more strongly in a bond (electronegativity 1.17 against 1.14).
Side by side
| Neodymium | Samarium | |
|---|---|---|
| Atomic number | 60 | 62 |
| Symbol | Nd | Sm |
| Family | Lanthanide | Lanthanide |
| Group / period | 3 / 6 | 3 / 6 |
| State at room temperature | Solid | Solid |
| Atomic mass | 144.242 u | 150.362 u |
| Density | 7.01 g/cm³ | 7.52 g/cm³ |
| Melting point | 1024 °C | 1072 °C |
| Boiling point | 3074 °C | 1900 °C |
| Electronegativity | 1.14 | 1.17 |
| First ionisation energy | 533.1 kJ/mol | 544.5 kJ/mol |
| Electron configuration | [Xe] 4f4 6s2 | [Xe] 4f6 6s2 |
| Discovered by | Carl Auer von Welsbach | Lecoq de Boisbaudran |
Neodymium
Neodymium is the reason a magnet the size of a fingernail can hold up a spanner. Alloyed with iron and boron, it forms the most powerful permanent magnets ever made, and they are everywhere: inside phone speakers, headphones and hard drives, and, in far larger quantities, in the motors of electric cars and the generators atop wind turbines.
- Neodymium-iron-boron magnets, invented in 1984, are the strongest type of permanent magnet commercially available.
- A single large wind turbine generator can contain several hundred kilograms of neodymium in its magnets.
Samarium
Ask an engineer about samarium and they will probably mention magnets. Samarium cobalt magnets were the first of the modern super strong permanent magnets, and although neodymium magnets have since overtaken them in raw strength, samarium cobalt still wins where things get hot. That single property keeps this otherwise obscure lanthanide in demand for aerospace, motors and sensors.
- Samarium-147 decays so slowly, with a half-life around a hundred billion years, that geologists use it to date some of the oldest rocks on Earth and meteorites from the early solar system.
- Samarium cobalt magnets keep their strength at temperatures where neodymium magnets lose theirs, which is why they are used in jet engines and satellites.
Colour the bubbles by density or melting point and the difference jumps out.
More comparisons
Data from Periodic-Table-JSON (CC BY-SA); temperatures rounded to the nearest degree. Written by Anthony.