Neodymium at a glance
- Atomic number
- 60
- Symbol
- Nd
- Atomic mass
- 144.24 u
- Category
- Lanthanide
- Period
- 6
- Electron configuration
- [Xe] 4f 4 6s 2
- State at 25 °C
- Solid
- Melting point
- 1024 °C
- Boiling point
- 3074 °C
- Density
- 7.007 g/cm³
- Electronegativity
- 1.14
- 1st ionization energy
- 533 kJ/mol
- Oxidation states
- +3
- Discovered
- 1885
Atomic structure
A neutral neodymium atom has 60 protons and 60 electrons, and its most common isotope carries about 82 neutrons. One atom weighs about 2.4 × 10⁻²⁵ kg, so a mole of neodymium (6.022 × 10²³ atoms) weighs 144.24 g. That nucleus holds 1.37 neutrons for every proton. The electrons fill 6 shells (K 2, L 8, M 18, N 22, O 8, P 2), which gives the configuration [Xe] 4f 4 6s 2. As a f-block element, both its outer s electrons and its inner f electrons can take part in bonding, which is why it shows more than one oxidation state. It has 6 stable isotopes: Nd-142, Nd-143, Nd-145, Nd-146, Nd-148 and Nd-150. Its most common isotope, Nd-142, has the same mass number as Ce-142: isobars, nuclei of different elements with 142 nucleons each.
Physical properties
At room temperature (25 °C) neodymium is a solid. It melts at 1024 °C and boils at 3074 °C, so it stays liquid across a 2050-degree range. It stays solid in a candle flame (about 1000 °C) but would melt in molten iron (1538 °C). Its density is 7.007 g/cm³, 7.01 times as dense as water. Its atoms have a radius of about 185 pm (Praseodymium next door is 185 pm). In the solid, its atoms pack into a hexagonal close-packed lattice.
Chemical behaviour
Its electronegativity is 1.14 on the Pauling scale. Pulling off its outermost electron takes 533 kJ/mol. A bond between neodymium and chlorine would be mostly ionic, with an electronegativity difference of 2. Its common oxidation states are +3, so in compounds you will usually meet it as Nd³⁺. It shares much of its chemistry with the other lanthanides, especially its neighbours Cerium, Praseodymium, Promethium and Samarium.
Where it comes from
It makes up 41.5 mg/kg of Earth's crust, the 27th most abundant element there. It was first identified in 1885, making it the 72nd element to be discovered (counting the 11 known since antiquity together).