18 2 · 8 · 8

Argon, Ar, element 18

Noble gas· Period 3· Group 18· p-block

Configuration [Ne]3s23p6

Atomic weight
39.948Da
Phase
gas
Density
0.001633g/cm³
Melting point
83.81K -189.34 °C
Boiling point
87.302K -185.85 °C
Electronegativity
No data

Monatomic noble gas. Makes up 0.93% of the air. Colourless, odorless. Is inert and has no true compounds. Lord Rayleigh and Sir william Ramsey identified argon in 1894. 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 argon

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.
39.948Da
Source: mendeleev
Electron configuration
[Ne]3s23p6
Source: mendeleev
Uncertainty of the atomic weight
0.001Da
Source: mendeleev
Electron configuration in full The electron configuration with the noble-gas core written out.
1s22s22p63s23p6
Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.
2 · 8 · 8
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.

SubshellScreening σEffective charge Z − σ
1s0.492517.5075
2s5.769612.2304
2p3.991814.0082
3s10.24327.7568
3p11.23596.7641