Crom

24
Cr
Grupă
6
Perioadă
4
Bloc
d
Protoni
Electroni
Neutroni
24
24
28
Proprietăți Generale
Număr atomic
24
Masă atomică
51,9961
Numar de masa
52
Categorie
Metale de tranziție
Culoare
Argint
Radioactive
Nu
Din cuvântul grecesc chroma, culoare
Structură cristalină
Corp Centrat Cubic
Istoric
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.
Electroni pe nivelul de energie
2, 8, 13, 1
Configurație electronică
[Ar] 3d5 4s1
Cr
Chromium oxide was used by the Chinese in the Qin dynasty over 2,000 years ago
Proprietăți Fizice
Fază
Solid
Densitate
7,15 g/cm3
Punct de topire
2180,15 K | 1907 °C | 3464,6 °F
Punct de fierbere
2944,15 K | 2671 °C | 4839,8 °F
Energie de fuziune
20,5 kJ/mol
Energie de evaporare
339 kJ/mol
Căldură specifică
0,449 J/g·K
Abundența în scoarța Pământului
0,014%
Abundența în Univers
0,0015%
High
Credite imagine: 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
Proprietăți Atomice
Rază atomică
128 pm
Rază de covalență
139 pm
Electronegativitate
1,66 (Scara lui Pauling)
Potențial de ionizare
6,7665 eV
Volum molar
7,23 cm3/mol
Conductivitate termică
0,937 W/cm·K
Număr de oxidare
-2, -1, 1, 2, 3, 4, 5, 6
Aplicații
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
Izotopi
Izotopi stabili
50Cr, 52Cr, 53Cr, 54Cr
Izotopi instabili
42Cr, 43Cr, 44Cr, 45Cr, 46Cr, 47Cr, 48Cr, 49Cr, 51Cr, 55Cr, 56Cr, 57Cr, 58Cr, 59Cr, 60Cr, 61Cr, 62Cr, 63Cr, 64Cr, 65Cr, 66Cr, 67Cr