68ErErbium167.2593[Xe] 4f¹² 6s²
lanthanide

Erbium

Erbium is a chemical element in the lanthanide series, with symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements on Earth. As such, it is a rare earth element which is associated with several other rare elements in the mineral gadolinite from Ytterby in Sweden, where yttrium, ytterbium, and terbium were discovered.

Properties

At a glance

Atomic number
68
Atomic mass
167.2593 u
Phase
Solid
Density
9.066 g/cm³
Melting point
1,802 K
Boiling point
3,141 K
First ionization energy
589.3 kJ/mol
Electronegativity
1.24
Electron affinity
30.1 kJ/mol
Molar heat capacity
28.12 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

Erbium’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…

68 protons98 neutrons

Erbium-166: 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, erbium 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

Er

ErNeutral atom · no charge

A neutral erbium atom. Removing its first electron takes 589 kJ/mol.

Erbium’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 1.9× 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). Erbium’s first electron takes about 6.1 eV.
1001,00010,000100,0001,000,00010,000,000Shell 5Shell 4Shell 3Shell 2×1.9×1.1×1.7×2.2×415101520253035404550556065
Show the values as a table
ElectronShellEnergy (kJ/mol)× previousValue
16589–Measured
261,1502Estimated
352,1901.9Estimated
454,0931.9Estimated
556,2811.5Estimated
659,2631.5Calculated
7510,9991.2Calculated
8512,6401.1Calculated
9515,2451.2Calculated
10517,0781.1Calculated
11419,3941.1Calculated
12422,6741.2Calculated
13425,8581.1Calculated
14427,9811.1Calculated
15430,0071.1Calculated
16433,2871.1Calculated
17436,7611.1Calculated
18440,0411.1Calculated
19443,4181.1Calculated
20446,8921.1Calculated
21450,1721.1Calculated
22453,5491.1Calculated
23474,2941.4Calculated
24478,1531.1Calculated
25482,3021.1Calculated
26486,7401.1Calculated
27490,9861Calculated
28495,4241Calculated
294100,9241.1Calculated
304105,3621Calculated
314110,1861Calculated
324114,6251Calculated
334132,1851.2Calculated
344136,6231Calculated
354141,6401Calculated
364146,2721Calculated
374156,7891.1Calculated
384161,9021Calculated
394173,9631.1Calculated
404179,3181Estimated
413304,6041.7Calculated
423315,0251Calculated
433326,2171Calculated
443338,1811Calculated
453349,6631Calculated
463361,0481Calculated
473377,8371Calculated
483389,6081Calculated
493402,3441Calculated
503414,3081Calculated
513447,5951.1Calculated
523458,1121Calculated
533469,4981Calculated
543480,3041Calculated
553514,1701.1Calculated
563526,3271Calculated
573549,4841Calculated
583561,0621Calculated
5921,246,3982.2Calculated
6021,275,2471Calculated
6121,307,1831Calculated
6221,336,8041Calculated
6321,461,3671.1Calculated
6421,496,5841Calculated
6521,540,9671Calculated
6621,570,2561Calculated
6716,353,3894Calculated
6816,487,8171Calculated

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?

ErbiumOther lanthanidesOther elements

Density

9.07 g/cm³32nd highest of 99

Er

Melting point

1,802 K25th highest of 96

Er

Boiling point

3,141 K37th highest of 97

Er

Electronegativity

1.2426th lowest of 96

Er

First ionization energy

589 kJ/mol29th lowest of 99

Er

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.