5 2 · 3

Boron, B, element 5

Metalloid· Period 2· Group 13· p-block

Configuration [He]2s²2p¹

Atomic weight: 10.81Da
Phase: solid
Density: 2.34g/cm³
Melting point: 2,350.15K 2,077 °C
Boiling point: 4,273.15K 4,000 °C
Electronegativity: 2.04

An element of group 13 of the periodic table. There are two allotropes, amorphous boron is a brown power, but metallic boron is black. The metallic form is hard (9.3 on Mohs' scale) and a bad conductor in room temperatures. It is never found free in nature. Boron-10 is used in nuclear reactor control rods and shields. It was discovered in 1808 by Sir Humphry Davy and by J.L. Gay-Lussac and L.J. Thenard. 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

4 of 5 fields have a value for boron

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.: 10.81Da; Source: mendeleev
Electron configuration: [He]2s²2p¹; Source: mendeleev
Electron configuration in full The electron configuration with the noble-gas core written out.: 1s²2s²2p¹; Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.: 2 · 3; 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	0.3205	4.6795
2s	2.4238	2.5762
2p	2.5786	2.4214