Cr
Chromium is a hard, lustrous transition metal valued for its mirror finish and corrosion resistance.
Physical Properties
| Atomic Mass | 51.996 u |
| Density | 7.15 g/cm³ |
| Melting Point | 2180.0 K |
| Boiling Point | 2944.0 K |
| Appearance | Steely-gray, lustrous, hard metallic |
| State at Room Temp | Solid |
Chemical Properties
| Electronegativity | 1.66 (Pauling) |
| 1st Ionization Energy | 652.9 kJ/mol |
| Electron Affinity | 65.2 kJ/mol |
| Oxidation States | +1, +2, +3, +4, +5, +6 |
Atomic Properties
| Electron Configuration | [Ar] 3d5 4s1 |
| Atomic Radius | 128.0 pm |
| Covalent Radius | 139.0 pm |
| Van der Waals Radius | 189.0 pm |
Discovery
| Discovered By | Louis Nicolas Vauquelin |
| Discovery Year | 1797 |
| Location | Paris, France |
| Named After | Greek 'chroma' meaning color, due to its many colorful compounds |
About Chromium
Chromium is a steely-gray, lustrous, hard metal that takes a high polish. It is remarkable for its resistance to tarnishing. It has an unusual electronic configuration with only one 4s electron due to the stability of a half-filled 3d shell.
Uses & Applications
Stainless steel, chrome plating, pigments, leather tanning, and catalysts.
Fun Fact
Chromium has an anomalous electron configuration -- it 'steals' an electron from 4s to give a half-filled 3d orbital.
Isotopes
| Mass Number | Abundance | Half-Life | Stable |
| 50 | 0.04345% | - | Yes |
| 52 | 0.83789% | - | Yes |
| 53 | 0.09501% | - | Yes |
| 54 | 0.02365% | - | Yes |
Electron Configuration
[Ar] 3d5 4s1