85 predicted 2 · 8 · 18 · 32 · 18 · 7

Astatine, At, element 85

Halogen· Period 6· Group 17· p-block

Configuration [Xe]4f¹⁴5d¹⁰6s²6p⁵

Atomic weight: 210Da
Phase: solid, predicted
Density: 8.93g/cm³, predicted
Melting point: 575.15K 302 °C
Boiling point: No data
Electronegativity: 2.2

Radioactive halogen element. Occurs naturally from uranium and thorium decay. At least 20 known isotopes. At-210, the most stable, has a half-life of 8.3 hours. Synthesized by nuclear bombardment in 1940 by D.R. Corson, K.R. MacKenzie and E. Segre at the University of California. 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

4 of 5 fields have a value for astatine

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.: 210Da; Source: mendeleev
Electron configuration: [Xe]4f¹⁴5d¹⁰6s²6p⁵; Source: mendeleev
Electron configuration in full The electron configuration with the noble-gas core written out.: 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰4f¹⁴5s²5p⁶5d¹⁰6s²6p⁵; Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.: 2 · 8 · 18 · 32 · 18 · 7; Source: Worked outfrom electron configuration

No data uncertainty of the atomic weight.

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	1.6446	83.3554
2s	22.3324	62.6676
2p	4.5524	80.4476
3s	24.6481	60.3519
3p	23.5024	61.4976
3d	13.4155	71.5845
4s	35.6644	49.3356
4p	36.516	48.484
4d	37.9504	47.0496
4f	37.7596	47.2404
5s	52.0665	32.9335
5p	53.96	31.04
5d	58.661	26.339
6s	67.7002	17.2998
6p	69.8368	15.1632