Ytterbium at a glance
- Atomic number
- 70
- Symbol
- Yb
- Atomic mass
- 173.05 u
- Category
- Lanthanide
- Period
- 6
- Electron configuration
- [Xe] 4f 14 6s 2
- State at 25 °C
- Solid
- Melting point
- 823.9 °C
- Boiling point
- 1196 °C
- Density
- 6.965 g/cm³
- Electronegativity
- 1.1
- 1st ionization energy
- 603 kJ/mol
- Oxidation states
- +3, +2
- Discovered
- 1878
Atomic structure
A neutral ytterbium atom has 70 protons and 70 electrons, and its most common isotope carries about 104 neutrons. One atom weighs about 2.87 × 10⁻²⁵ kg, so a mole of ytterbium (6.022 × 10²³ atoms) weighs 173.05 g. That nucleus holds 1.49 neutrons for every proton, typical of heavy nuclei, which need extra neutrons to hold together against the protons' repulsion. The electrons fill 6 shells (K 2, L 8, M 18, N 32, O 8, P 2), which gives the configuration [Xe] 4f 14 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 7 stable isotopes: Yb-168, Yb-170, Yb-171, Yb-172, Yb-173, Yb-174 and Yb-176. No other element has a stable isotope with mass number 174, so Yb-174 has no stable isobars; its neighbours on that line decay into it or away from it.
Physical properties
At room temperature (25 °C) ytterbium is a solid. It melts at 823.9 °C and boils at 1196 °C, so it stays liquid across a 372-degree range. It stays solid in a hot kitchen oven but would melt in a candle flame (about 1000 °C). Its density is 6.965 g/cm³, 6.96 times as dense as water. Its atoms have a radius of about 175 pm (Thulium next door is 175 pm). In the solid, its atoms pack into a face-centred cubic lattice.
Chemical behaviour
Its electronegativity is 1.1 on the Pauling scale. Pulling off its outermost electron takes 603 kJ/mol. A bond between ytterbium and chlorine would be mostly ionic, with an electronegativity difference of 2.1. Its common oxidation states are +3, +2, so in compounds you will usually meet it as Yb³⁺ and Yb²⁺. It shares much of its chemistry with the other lanthanides, especially its neighbours Erbium, Thulium and Lutetium.
Where it comes from
It makes up 3.2 mg/kg of Earth's crust, the 45th most abundant element there. It was first identified in 1878, making it the 66th element to be discovered (counting the 11 known since antiquity together).