Lutetium (Lu)
Lutetium is element 71, a lanthanide in the lanthanide series (period 6). A neutral atom has 71 protons, 104 neutrons and 71 electrons, 2 of them valence electrons.
Lanthanide- Atomic number
- 71
- Atomic mass
- 174.97 u
- Valence electrons
- 2*
- Protons · neutrons
- 71 · 104
- Electrons per shell
- 2, 8, 18, 32, 9, 2
- At room temperature
- solid
Bohr model of lutetium
The Bohr model draws lutetium as a nucleus of 71 protons and 104 neutrons, with its 71 electrons on 6 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 9 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 lutetium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹
Short form (noble gas notation): [Xe] 6s² 4f¹⁴ 5d¹. The [Xe] stands for the electrons of xenon, the noble gas before it.
How many valence electrons does lutetium have?
Lutetium has 2 valence electrons.
Lutetium 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 d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 71 | equal to the atomic number |
|---|---|---|
| Electrons | 71 | equal to the protons in a neutral atom |
| Neutrons | 104 | mass number 175 − 71 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.
Lutetium properties
| Symbol | Lu |
|---|---|
| Category | Lanthanide |
| Group · period · block | — · 6 · d |
| Atomic mass | 174.97 u |
| State at 25 °C | solid |
| Melting point | 1,936 K (1,660 °C, 3,030 °F) |
| Boiling point | 3,675 K (3,400 °C, 6,160 °F) |
| Density | 9.84 g/cm³ |
| Electronegativity (Pauling) | 1.27 |
| Atomic radius | 221 pm |
| First ionization energy | 5.426 eV |
| Electron affinity | — |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | 1907 by Georges Urbain |
Where lutetium sits on the periodic table
Lanthanides: Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium.
Questions about lutetium
How many valence electrons does lutetium have?
Lutetium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does lutetium have?
A neutral lutetium atom has 71 protons and 71 electrons. Its most common form has about 104 neutrons (mass number 175 − 71 protons).
What is the electron configuration of lutetium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹, written in short form as [Xe] 6s² 4f¹⁴ 5d¹.
What does the Bohr model of lutetium look like?
A nucleus of 71 protons and 104 neutrons, circled by 6 electron shells holding 2, 8, 18, 32, 9, 2 electrons.
What is the atomic number of lutetium?
71. The atomic number is the number of protons in the nucleus, and it is what makes an atom lutetium.