Fermium (Fm)
Fermium is element 100, an actinide in the actinide series (period 7). A neutral atom has 100 protons, 157 neutrons and 100 electrons, 2 of them valence electrons.
Actinide- Atomic number
- 100
- Atomic mass
- [257] u
- Valence electrons
- 2*
- Protons · neutrons
- 100 · 157
- Electrons per shell
- 2, 8, 18, 32, 30, 8, 2
- At room temperature
- solid
Bohr model of fermium
The Bohr model draws fermium as a nucleus of 100 protons and 157 neutrons, with its 100 electrons on 7 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 30 in shell 5, 8 in shell 6, 2 in shell 7. Press Build the atom to watch the shells fill from the inside out. The outer ring (the Q 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 fermium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹²
Short form (noble gas notation): [Rn] 7s² 5f¹². The [Rn] stands for the electrons of radon, the noble gas before it.
How many valence electrons does fermium have?
Fermium has 2 valence electrons.
Fermium is a actinide, so its valence electrons are less clear-cut than for main-group elements. It has 2 electrons in its outermost shell (shell 7), and electrons in its inner f and d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 100 | equal to the atomic number |
|---|---|---|
| Electrons | 100 | equal to the protons in a neutral atom |
| Neutrons | 157 | mass number 257 − 100 protons (for its longest-lived isotope, Fm-257) |
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.
Fermium properties
| Symbol | Fm |
|---|---|
| Category | Actinide |
| Group · period · block | — · 7 · f |
| Atomic mass | [257] u |
| State at 25 °C | solid |
| Melting point | 1,800 K (1,530 °C, 2,780 °F) |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | 1.3 |
| Atomic radius | — |
| First ionization energy | 6.5 eV |
| Electron affinity | — |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | 1952 by Lawrence Berkeley National Laboratory |
Where fermium sits on the periodic table
Actinides: Actinium, Thorium, Protactinium, Uranium, Neptunium, Plutonium, Americium, Curium.
Questions about fermium
How many valence electrons does fermium have?
Fermium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does fermium have?
A neutral fermium atom has 100 protons and 100 electrons. Its most common form has about 157 neutrons (mass number 257 − 100 protons).
What is the electron configuration of fermium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹², written in short form as [Rn] 7s² 5f¹².
What does the Bohr model of fermium look like?
A nucleus of 100 protons and 157 neutrons, circled by 7 electron shells holding 2, 8, 18, 32, 30, 8, 2 electrons.
What is the atomic number of fermium?
100. The atomic number is the number of protons in the nucleus, and it is what makes an atom fermium.