27 - Cobalt transition metal
Discovered by Georg Brandt in 1735
Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt in the Earth's crust is found only in chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal.
H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
57-71 La-Lu Lanthanides
89-103 Ac-Lr Actinides
| Shell | Electrons | Orbitals |
|---|---|---|
| 1 | 2 | 2 in 1s |
| 2 | 8 | 2 in 2s + 6 in 2p |
| 3 | 15 | 2 in 3s + 6 in 3p + 7 in 3d |
| 4 | 2 | 2 in 4s |
hard lustrous gray metal Appearance
58.9 u Atomic Mass
1.35 Å Atomic Radius
3.2k K Boiling Point
9 Group
2, 3 Common Oxidation States
1.26 Å Covalent Radius
8.9 g/cm³ Density
63.9 kJ/mol Electron Affinity
1s2 2s2 2p6 3s2 3p6 4s2 3d7 Electron Configuration
[Ar] 3d7 4s2 Electron Configuration (semantic)
1.88 Electronegativity
27 Electrons
7.88 eV First Ionization Energy
1, 2, 3, 4 ICSD Oxidation States
760.4, 1648, 3232, 4950, 7670, 9840, 12440, 15230, 17959, 26570, 29400, 32400, 36600, 39700, 42800, 49396, 52737, 134810, 145170, 154700, 167400, 178100, 189300, 204500, 214100, 920870, 966023 kJ/mol Ionization Energies
1.77k K Melting Point
64 Mendeleev Number
24.8 J/(mol·K) Molar Heat
4 Number of Shells
32 Neutrons
27 Atomic Number
14 Number of Isotopes
-1, 1, 2, 3, 4, 5 Oxidation States
4 Period
Solid Phase
27 Protons
2, 8, 15, 2 Electron Shell Occupations