19 2 · 8 · 8 · 1

Potassium, K, element 19

Alkali metal· Period 4· Group 1· s-block

Configuration [Ar]4s¹

Atomic weight: 39.0983Da
Phase: solid
Density: 0.89g/cm³
Melting point: 336.65K 63.5 °C
Boiling point: 1,032.15K 759 °C
Electronegativity: 0.82

Soft silvery metallic element belonging to group 1 of the periodic table (alkali metals). Occurs naturally in seawater and a many minerals. Highly reactive, chemically, it resembles sodium in its behavior and compounds. Discovered by Sir Humphry Davy in 1807. Description from mendeleev.

Back to the table

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 potassium

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.: 39.0983Da; Source: mendeleev
Electron configuration: [Ar]4s¹; Source: mendeleev
Uncertainty of the atomic weight: 1×10⁻⁴Da; Source: mendeleev
Electron configuration in full The electron configuration with the noble-gas core written out.: 1s²2s²2p⁶3s²3p⁶4s¹; Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.: 2 · 8 · 8 · 1; 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	0.5105	18.4895
2s	5.9938	13.0062
2p	3.9728	15.0272
3s	10.3201	8.6799
3p	11.2744	7.7256
4s	15.5048	3.4952