Atomic number:33
Group numbers:15
Period:4
Electronic configuration:[Ar] 3d10 4s2 4p3
Formal oxidation number:-3 +3 +5
Electronegativities:2.18
Atomic radius / pm:124.5
Relative atomic mass:74.92160 ± 0.00002
Arsenic was discovered by Albertus Magnus (DE) in 1250. The origin of the name comes from the Greek word arsenikon meaning yellow orpiment. It is a steel-grey, brittle semi-metal that resists water, acids and alkalis. It tarnishes in air, burns in oxygen and is highly toxic by inhalation or ingestion. Arsenic is found in mispickel (arsenopyrite). Many of its compounds are deadly poison and used as weed killer and rat poison. Some compounds, called arsenides, are used in the manufacture of paints, wallpapers and ceramics. It is also used in semiconductors
Crystal structure:
rhombohedral
Unit-cell dimensions / pm:
a=413.18, α=54°10'
Space group:
R3m
Density / g dm-3:5780 (alpha, 293 K)
4700 (beta, 293 K)
Molar volume / cm3mol-1:12.96 (alpha, 293 K)
15.94 (beta, 293 K)
Electrical resistivity / μΩcm:33.3 (20 °C)
Thermal conductivity / W m-1K-1:50
Melting point / °C:817
Boiling point / °C:614
Heat of fusion / kJ mol-1:27.7
Heat of vaporization / kJ mol-1:31.9
Heat of atomization / kJ mol-1:301.42
1st ionization energy / kJ mol-1:944.46
2nd ionization energy / kJ mol-1:1797.82
3rd ionization energy / kJ mol-1:2735.48
in the atmosphere / ppm:-
in the Earth's crust / ppm:1
in the oceans / ppm:0.003
AsO+ + 3H2O+0.55 H3AsO3 + H2O+0.559 H3AsO3 + H2O+0.577 (1 mol dm-3 HCl) H3AsO3 + H2O+0.577 (1 mol dm-3 HClO4) H3AsO3 + H2O+0.666 H3AsO3 + H2O+0.881 H2AsO3- + H2O+0.609 H2AsO3- + 4OH-- 0.67 As2O3(s) + 5H2O+0.58 As2O3(s) + 5H2O+0.687 As2O3(s) + 5H2O+0.901 As2O3(s) + 5H2O+1.27 As(s) + 4H2O+0.648 2As(s) + 3H2O+0.234 As(s) + H2O+0.254 As(s) + 3H2O+0.248 As(s) + 3H2O+0.429 As(s) + 4OH-- 0.68 AsH3(g)- 0.608
32 Germanium <= 33 Arsenic => 34 Selenium