Iron (Fe)
Iron is element 26, a transition metal in group 8, period 4. A neutral atom has 26 protons, 30 neutrons and 26 electrons, 2 of them valence electrons.
Transition metal- Atomic number
- 26
- Atomic mass
- 55.84 u
- Valence electrons
- 2*
- Protons · neutrons
- 26 · 30
- Electrons per shell
- 2, 8, 14, 2
- At room temperature
- solid
Bohr model of iron
The Bohr model draws iron as a nucleus of 26 protons and 30 neutrons, with its 26 electrons on 4 circular shells: 2 in shell 1, 8 in shell 2, 14 in shell 3, 2 in shell 4. Press Build the atom to watch the shells fill from the inside out. The outer ring (the N 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 iron
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶
Short form (noble gas notation): [Ar] 4s² 3d⁶. The [Ar] stands for the electrons of argon, the noble gas before it.
How many valence electrons does iron have?
Iron has 2 valence electrons.
Iron is a transition metal, so its valence electrons are less clear-cut than for main-group elements. It has 2 electrons in its outermost shell (shell 4), and electrons in its inner d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 26 | equal to the atomic number |
|---|---|---|
| Electrons | 26 | equal to the protons in a neutral atom |
| Neutrons | 30 | mass number 56 − 26 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.
Iron properties
| Symbol | Fe |
|---|---|
| Category | Transition metal |
| Group · period · block | 8 · 4 · d |
| Atomic mass | 55.84 u |
| State at 25 °C | solid |
| Melting point | 1,811 K (1,540 °C, 2,800 °F) |
| Boiling point | 3,134 K (2,860 °C, 5,180 °F) |
| Density | 7.874 g/cm³ |
| Electronegativity (Pauling) | 1.83 |
| Atomic radius | 194 pm |
| First ionization energy | 7.902 eV |
| Electron affinity | 0.163 eV |
| Oxidation states | +3, +2 |
| Common ion charge | +3, +2 |
| Discovered | Known since ancient times |
Where iron sits on the periodic table
Group 8: Ruthenium, Osmium, Hassium.
Questions about iron
How many valence electrons does iron have?
Iron has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does iron have?
A neutral iron atom has 26 protons and 26 electrons. Its most common form has about 30 neutrons (mass number 56 − 26 protons).
What is the electron configuration of iron?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶, written in short form as [Ar] 4s² 3d⁶.
What does the Bohr model of iron look like?
A nucleus of 26 protons and 30 neutrons, circled by 4 electron shells holding 2, 8, 14, 2 electrons.
What is the atomic number of iron?
26. The atomic number is the number of protons in the nucleus, and it is what makes an atom iron.