Erbium (Er)
Erbium is element 68, a lanthanide in the lanthanide series (period 6). A neutral atom has 68 protons, 99 neutrons and 68 electrons, 2 of them valence electrons.
Lanthanide- Atomic number
- 68
- Atomic mass
- 167.26 u
- Valence electrons
- 2*
- Protons · neutrons
- 68 · 99
- Electrons per shell
- 2, 8, 18, 30, 8, 2
- At room temperature
- solid
Bohr model of erbium
The Bohr model draws erbium as a nucleus of 68 protons and 99 neutrons, with its 68 electrons on 6 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 30 in shell 4, 8 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 erbium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹²
Short form (noble gas notation): [Xe] 6s² 4f¹². The [Xe] stands for the electrons of xenon, the noble gas before it.
How many valence electrons does erbium have?
Erbium has 2 valence electrons.
Erbium 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 f and d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 68 | equal to the atomic number |
|---|---|---|
| Electrons | 68 | equal to the protons in a neutral atom |
| Neutrons | 99 | mass number 167 − 68 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.
Erbium properties
| Symbol | Er |
|---|---|
| Category | Lanthanide |
| Group · period · block | — · 6 · f |
| Atomic mass | 167.26 u |
| State at 25 °C | solid |
| Melting point | 1,802 K (1,530 °C, 2,780 °F) |
| Boiling point | 3,141 K (2,870 °C, 5,190 °F) |
| Density | 9.07 g/cm³ |
| Electronegativity (Pauling) | 1.24 |
| Atomic radius | 235 pm |
| First ionization energy | 6.108 eV |
| Electron affinity | — |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | 1843 by Carl Gustaf Mosander |
Where erbium sits on the periodic table
Lanthanides: Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium.
Questions about erbium
How many valence electrons does erbium have?
Erbium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does erbium have?
A neutral erbium atom has 68 protons and 68 electrons. Its most common form has about 99 neutrons (mass number 167 − 68 protons).
What is the electron configuration of erbium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹², written in short form as [Xe] 6s² 4f¹².
What does the Bohr model of erbium look like?
A nucleus of 68 protons and 99 neutrons, circled by 6 electron shells holding 2, 8, 18, 30, 8, 2 electrons.
What is the atomic number of erbium?
68. The atomic number is the number of protons in the nucleus, and it is what makes an atom erbium.