Chemical element · Atomic number 33
Arsenic
Arsenic in the periodic table: atomic number 33, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Metalloid
solid
74.92159 u
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Atomic classification
Shell occupancy
Arsenic in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 8 electrons
- M · n=3
- 18 electrons
- N · n=4
- 5 electrons
- Electron configuration
- [Ar]4s2 3d10 4p3
- Electrons per shell
- 2 · 8 · 18 · 5
- Group
- 15
- Period
- 4
- Block
- P
- Element category
- Metalloid
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Physical and chemical properties
- Atomic mass
- 74.92159 u
- Standard state
- solid
- Density
- 5.776 g/cm³
- Melting point
- 1,090 K
- Boiling point
- 887 K
- Electronegativity
- 2.18 (Pauling)
- First ionisation energy
- 9.815 eV
- Oxidation states
- +5, +3, -3
- Discovery
- known since antiquity
Safety and periodic classification
Safety
Safe handling cannot be inferred from Arsenic's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Arsenic is in period 4, group 15 and the P block. Its direct neighbours by atomic number are Germanium and Selenium. The recorded Pauling electronegativity is 2.18. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.