Krom

24
Cr
Gruppe
6
Periode
4
Blok
d
Protons
Electrons
Neutrons
24
24
28
General Properties
Atomnummer
24
Atommasse
51,9961
Mass Number
52
Kategori
Overgangsmetaller
Farve
Silver
Radioactive
Nej
From the Greek word chroma, color
Krystalstruktur
Rumcentreret Kubisk
History
In 1797, Louis Nicolas Vauquelin received samples of crocoite ore.

In 1798, Vauquelin discovered that he could isolate metallic chromium by heating the oxide in a charcoal oven, making him the discoverer of the element.

Vauquelin was also able to detect traces of chromium in precious gemstones, such as ruby or emerald.
Elektroner i hver skal
2, 8, 13, 1
Elektronkonfiguration
[Ar] 3d5 4s1
Cr
Chromium oxide was used by the Chinese in the Qin dynasty over 2,000 years ago
Physical Properties
Tilstandsform
Fast stof
Massefylde
7,15 g/cm3
Smeltepunkt
2180,15 K | 1907 °C | 3464,6 °F
Kogepunkt
2944,15 K | 2671 °C | 4839,8 °F
Smeltevarme
20,5 kJ/mol
Fordampningsvarme
339 kJ/mol
Varmefylde
0,449 J/g·K
Abundance in Earth's crust
0,014%
Abundance in Universe
0,0015%
High
Billede akkrediteringer: Wikimedia Commons (Alchemist-hp)
High purity chromium crystals, produced by chemical transport reaction through decomposition of chromium iodides, as well as a high purity chromium cube for comparison
CAS Number
7440-47-3
PubChem CID Number
23976
Atomic Properties
Atomradius
128 pm
Kovalent radius
139 pm
Elektronegativitet
1,66 (Paulings skala)
Ionization Potential
6,7665 eV
Atomic Volume
7,23 cm3/mol
Varmeledningsevne
0,937 W/cm·K
Oxidationstrin
-2, -1, 1, 2, 3, 4, 5, 6
Applications
Chromium is used to harden steel, manufacture stainless steel, and form many useful alloys.

It is mostly used in plating to produce a hard, beautiful surface and to prevent corrosion.

The metal is also widely used as a catalyst.

Chromium compounds are valued as pigments for their vivid green, yellow, red and orange colors.
In larger amounts, chromium can be toxic and carcinogenic
Isotoper
Stable Isotopes
50Cr, 52Cr, 53Cr, 54Cr
Unstable Isotopes
42Cr, 43Cr, 44Cr, 45Cr, 46Cr, 47Cr, 48Cr, 49Cr, 51Cr, 55Cr, 56Cr, 57Cr, 58Cr, 59Cr, 60Cr, 61Cr, 62Cr, 63Cr, 64Cr, 65Cr, 66Cr, 67Cr