3374.922AsArsenic
Arsenic (As) — element 33metalloid · group 15, period 4
Arsenic is a chemical element with the symbol As and atomic number 33. It is a metalloid in group 15, period 4 of the periodic table (the p-block), with a standard atomic mass of 74.922 u. At room temperature (25 °C) arsenic is a solid.
💡 Known for: An infamous poison that is also used in semiconductors such as gallium arsenide.
# Arsenic properties
| Symbol | As |
|---|---|
| Atomic number | 33 |
| Atomic mass | 74.922 u |
| Category | metalloid |
| Group | 15 |
| Period | 4 |
| Block | p-block |
| Electron configuration | [Ar] 3d¹⁰ 4s² 4p³ |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³ |
| Electrons per shell | 2, 8, 18, 5 |
| Protons / electrons | 33 / 33 |
| State at 25 °C | solid |
| Melting point | 1090 K (816.9 °C, 1502.3 °F) |
| Boiling point | 887 K (613.9 °C, 1136.9 °F) |
| Density | 5.776 g/cm³ |
| Electronegativity (Pauling) | 2.18 |
| First ionization energy | 9.789 eV |
| Atomic radius | 114 pm |
| Discovered | known since ancient times |
# Electron configuration of arsenic
The electron configuration of arsenic is [Ar] 3d¹⁰ 4s² 4p³, written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³. Its 33 electrons fill 4 shells as 2, 8, 18, 5, so the outermost shell holds 5 electrons. As a group 15 element, arsenic has 5 valence electrons.
# Related elements
GeGermaniumprevious elementSeSeleniumnext elementNNitrogengroup 15PPhosphorusgroup 15SbAntimonygroup 15BiBismuthgroup 15McMoscoviumgroup 15BBoronmetalloidSiSiliconmetalloidTeTelluriummetalloid
# Arsenic FAQ
What is the atomic number of arsenic?
The atomic number of arsenic is 33: every arsenic atom has 33 protons in its nucleus. Its symbol is As.
What is the atomic mass of arsenic?
The standard atomic mass of arsenic is 74.922 u.
What is the electron configuration of arsenic?
Arsenic's electron configuration is [Ar] 3d¹⁰ 4s² 4p³ (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³), with 2, 8, 18, 5 electrons per shell.
Is arsenic a metal?
No. Arsenic is a metalloid, with properties between those of metals and nonmetals.
What is the melting point of arsenic?
Arsenic melts at 1090 K (816.9 °C, 1502.3 °F) and boils at 887 K (613.9 °C, 1136.9 °F).
What is arsenic used for / known for?
An infamous poison that is also used in semiconductors such as gallium arsenide.