Element 33
Arsenic (As)
Arsenic (As) is element 33 of the periodic table, a metalloid in period 4, group 15 (p-block) with an atomic mass of 74.922 and is a solid at standard conditions.
At a glance
- Atomic number
- 33
- Symbol
- As
- Atomic mass
- 74.922 u
- Category
- Metalloids
- Period
- 4
- Group
- 15
- Block
- p-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3
- Shorthand configuration
- [Ar] 3d10 4s2 4p3
- Electrons per shell
- 2, 8, 18, 5
- Oxidation states
- -3, -2, -1, +1, +2, +3, +4, +5
Physical properties
- Melting point
- 1,090 K (816.85 °C)
- Boiling point
- 887 K (613.85 °C)Arsenic sublimes - it passes straight from solid to vapour at 887 K. It melts at 1090 K only under roughly 3.7 MPa, which is why the boiling point is the lower number.
- Density
- 5.776 g/cm³
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 2.18
- Atomic radius
- 114 pm
- Covalent radius
- 119 pm
- Van der Waals radius
- 185 pm
- First ionization energy
- 947 kJ/mol
- Electron affinity
- 78 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| As-75 | 74.9216 | 100% | Stable |
Common uses
- Semiconductors
- Wood preservation
- Alloys
- Pesticides
Discovery
- Year
- 1250
- Discovered by
- Albertus Magnus
- Country
- Germany
Frequently asked questions
- Is arsenic a metal?
- Arsenic is a metalloid, which means it shows properties of both metals and nonmetals.
- How many protons does arsenic have?
- Arsenic has 33 protons. Its atomic number is 33, which is also the number of electrons in a neutral atom of arsenic.
- What group and period is arsenic in?
- Arsenic is in group 15 and period 4 of the periodic table, in the p-block.
- What is the atomic mass of arsenic?
- The atomic mass of arsenic is 74.922 u (unified atomic mass units).
Keep exploring
Arsenic's row is on the printable element property sheet, and its tile is on the periodic table wall chart - the same numbers as above, laid out for A4 or A3 paper.