71LuLutetium174.96681[Xe] 4f¹⁴ 5d¹ 6s²
lanthanide

Lutetium

Lutetium is a chemical element with symbol Lu and atomic number 71. It is a silvery white metal, which resists corrosion in dry, but not in moist air. It is considered the first element of the 6th-period transition metals and the last element in the lanthanide series, and is traditionally counted among the rare earths.

Properties

At a glance

Atomic number
71
Atomic mass
174.96681 u
Phase
Solid
Density
9.841 g/cm³
Melting point
1,925 K
Boiling point
3,675 K
First ionization energy
523.5 kJ/mol
Electronegativity
1.27
Electron affinity
33.4 kJ/mol
Molar heat capacity
26.86 J/(mol·K)
Period
6
Appearance
silvery white

Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.

Electronic structure

Lutetium’s orbitals use a hydrogen-like approximation. Every orbital of each visible subshell is shown: in Shapes as the surface holding half its probability, with light and dark shades for opposite signs of the wavefunction; in Cloud as dots where its electrons are likely to be. Sizes are stepped by shell, like the Shell model.

Electrons by shell
Electron configuration

54 is the [Xe] core total across five shells.

Preparing the orbital view…

71 protons104 neutrons

Lutetium-175: its most common form in nature, or its longest-lived if it has none. The nucleus is drawn far too big: it’s about 100,000 times smaller than the atom.

States of matter

Turn up the heat

298 KK stands for kelvin, the temperature scale used in science. It starts at absolute zero (0 K), the coldest temperature possible, so it has no negative numbers and no degree sign.

A step of 1 K is the same size as 1 °C, so the two scales are always 273.15 apart. Fahrenheit is different: its degrees are smaller and it starts elsewhere, so water freezes at 273.15 K, 0 °C and 32 °F.25 °C · 77 °FSolid

At this temperature, lutetium is a solid.

At normal atmospheric pressure (1 atm). The temperature scale is logarithmic. The particle box is schematic: real samples hold vastly more atoms, and spacing and speeds are not to scale.

Ionization energy

Pull the electrons off

Lu

LuNeutral atom · no charge

A neutral lutetium atom. Removing its first electron takes 524 kJ/mol.

Lutetium’s outer shell holds 2 electrons. Electron 3 is the first from an inner shell: it sits closer to the nucleus with less shielding, so removing it takes 1.5× as much energy as the one before. Each dashed line on the chart marks another jump, into a shell even closer to the nucleus.

Shell 1Shell 2Shell 3Shell 4Shell 5Shell 6MeasuredEstimated or calculatedEnergy in kJ/molkJ/mol (kilojoules per mole) is the energy to remove that electron from every atom in a mole of them: about 602 sextillion (6.02 × 10²³) atoms. For a single atom, divide by 96.485 to get electronvolts (eV). Lutetium’s first electron takes about 5.4 eV.
1001,00010,000100,0001,000,00010,000,000Shell 5Shell 4Shell 3Shell 2×1.5×1.2×1.7×2.2×41510152025303540455055606570
Show the values as a table
ElectronShellEnergy (kJ/mol)× previousValue
16524–Measured
261,3632.6Estimated
352,0221.5Measured
454,3662.2Estimated
556,4451.5Estimated
659,4561.5Calculated
7511,2891.2Calculated
8513,1221.2Calculated
9515,3411.2Calculated
10517,8501.2Calculated
11519,7791.1Calculated
12422,9641.2Calculated
13426,6301.2Calculated
14429,4281.1Calculated
15431,6471.1Calculated
16434,8311.1Calculated
17438,4981.1Calculated
18442,2611.1Calculated
19445,9271.1Calculated
20450,1721.1Calculated
21454,0321.1Calculated
22457,8911.1Calculated
23460,7861.1Calculated
24464,6451.1Calculated
25468,7941.1Calculated
26490,7931.3Calculated
27495,0381Calculated
28499,5731Calculated
294104,3011Calculated
304109,0281Calculated
314113,6601Calculated
324119,8351.1Calculated
334124,6591Calculated
344129,7731Calculated
354134,5971Calculated
364153,5081.1Calculated
374158,3321Calculated
384163,6391Calculated
394168,5601Calculated
404180,9101.1Calculated
414186,5061Calculated
424199,4351.1Calculated
434205,0801Estimated
443346,3821.7Calculated
453357,5751Calculated
463369,3461Calculated
473382,0821Calculated
483394,2391Calculated
493406,3001Calculated
503424,8251Calculated
513437,2721Calculated
523450,8761Calculated
533463,4191Calculated
543498,6361.1Calculated
553509,6361Calculated
563521,7931Calculated
573533,0811Calculated
583572,8331.1Calculated
593585,6661Calculated
603610,3661Calculated
613622,5231Calculated
6221,372,7932.2Calculated
6321,403,0901Calculated
6421,436,6671Calculated
6521,467,6381Calculated
6621,614,2001.1Calculated
6721,651,8291Calculated
6821,699,1071Calculated
6921,729,7941Calculated
7016,978,0964Calculated
7117,121,0371Calculated

Successive ionization energies of gas-phase atoms and ions from the NIST Atomic Spectra Database. Solid bars are measured; hatched bars were estimated from nearby measurements or calculated from quantum theory, as is usual for highly charged ions. Electrons are taken from the outermost shell first, a simplification: electrons in different subshells of the same shell also differ in energy. On the log scale each gridline is 10 times the one below.

Compared with other elements

How does it compare?

LutetiumOther lanthanidesOther elements

Density

9.84 g/cm³28th highest of 99

Lu

Melting point

1,925 K19th highest of 96

Lu

Boiling point

3,675 K22nd highest of 97

Lu

Electronegativity

1.2728th lowest of 96

Lu

First ionization energy

524 kJ/mol10th lowest of 99

Lu

Elements 1–99 from the reference data; heavier elements are left out because only a few atoms have ever been made, so their bulk properties are predictions. First ionization energies come from NIST. Density uses a logarithmic scale, because gases are around a thousand times less dense than solids; gas densities are at 0 °C and 1 atm. Melting and boiling points are at normal pressure. Everyday temperatures and light sources in the pictures are approximate. Hover over a dot to see the element, or click it to compare.

Keep exploring

Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.