27 2 · 8 · 15 · 2

Cobalt, Co, element 27

Transition metal· Period 4· Group 9· d-block

Configuration [Ar]3d⁷4s²

Atomic weight: 58.9332Da
Phase: solid
Density: 8.86g/cm³
Melting point: 1,768.15K 1,495 °C
Boiling point: 3,200.15K 2,927 °C
Electronegativity: 1.88

Light grey transition element. Some meteorites contain small amounts of metallic cobalt. Generally alloyed for use. Mammals require small amounts of cobalt salts. Cobalt-60, an artificially produced radioactive isotope of Cobalt is an important radioactive tracer and cancer-treatment agent. Discovered by G. Brandt in 1737. Description from mendeleev.

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The outermost shell: the valence electronsThe inner shellsThe nucleus One bead for each electron, on the ring of its shell, counted from the nucleus out. The rings turn at their own pace; the model is Bohr's picture of the atom, which places electrons in shells but not on true orbits.

Atomic properties

5 of 5 fields have a value for cobalt

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.: 58.93319Da; Source: mendeleev
Electron configuration: [Ar]3d⁷4s²; Source: mendeleev
Uncertainty of the atomic weight: 4×10⁻⁶Da; Source: mendeleev
Electron configuration in full The electron configuration with the noble-gas core written out.: 1s²2s²2p⁶3s²3p⁶3d⁷4s²; Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.: 2 · 8 · 15 · 2; Source: Worked outfrom electron configuration

Screening of each subshell

Clementi's screening constants: how much of the nucleus's charge the other electrons hide from an electron in each subshell. What is left is the effective nuclear charge it feels.

Subshell	Screening σ	Effective charge Z − σ
1s	0.6332	26.3668
2s	7.595	19.405
2p	3.9076	23.0924
3s	12.6777	14.3223
3p	13.5654	13.4346
3d	15.1446	11.8554
4s	21.4236	5.5764