Cr
Chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It has a standard atomic weight of 51.996, sits in period 4 and group 6, and is classified as a transition metal.
Properties
| Symbol | Cr |
|---|---|
| Atomic number | 24 |
| Standard atomic weight | 51.996 |
| Category | Transition metal |
| Group | 6 |
| Period | 4 |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d5 4s1 |
| Outer-shell electrons | 2 |
The figure of 51.996 is a standard atomic weight.
Compounds containing chromium
2 of the compounds in this reference contain Cr, listed by the fraction of their mass it makes up.
| Compound | Formula | Atoms | % by mass |
|---|---|---|---|
| chromium oxide | Cr2O3 | 2 | 68.4% |
| potassium dichromate | Cr2K2O7 | 2 | 35.3% |
Calculate with chromium
- Molar mass of any formula containing it
- Electron configuration, including ions
- Effective nuclear charge by Slater's rules
- Average atomic mass from isotope abundances
Group 6
Atomic weights are the IUPAC 2021 standard values, abridged to the conventional five significant figures. Group, period, category and electron configuration are derived from the atomic number rather than stored, so they cannot drift out of step with it.