Element 33
Arsenic
Metalloids
Arsenic (As) is in the p-block of the periodic table — group 15, period 4.
Arsenic is a chemical element with symbol As and atomic number 33.
Key data
- Atomic number
- 33
- Atomic mass
- 74.922 u
- Group / Period
- 15 / 4
- Block
- p-block
- Phase at STP
- Solid
- Density
- 5.727 g/cm³
- Melting point
- —
- Boiling point
- —
- Electron configuration
- [Ar] 3d10 4s2 4p3
Periodic table block
Arsenic is in the p-block (group 15, period 4). Elements land in the p-block when their highest-energy electrons fill a p subshell — this region holds most nonmetals, the metalloids, and the metals on the right of the table.
New to this? Periodic table blocks explained: s, p, d, and f
Common uses
- •Wood preservative
- •Semiconductor dopant
- •Toxic histories
Discovery
Year: Known since antiquity
Discovered by: Bronze Age
Frequently asked questions
What is the atomic number of Arsenic?
Arsenic has atomic number 33. Its symbol is As and its atomic mass is 74.922 u.
What category of element is Arsenic?
Arsenic is classified as metalloids. It sits in group 15, period 4 of the periodic table.
What block of the periodic table is Arsenic in?
Arsenic is in the p-block (group 15, period 4). Its highest-energy electrons occupy the p subshell — you can see this in its electron configuration, [Ar] 3d10 4s2 4p3.
What is Arsenic used for?
Common uses of Arsenic include: Wood preservative, Semiconductor dopant, Toxic histories.
When was Arsenic discovered?
Arsenic has been known since antiquity.
Play the game
Test your knowledge in The Lab
20-round element ID, cryptic 3-clue guesser, and an interactive periodic table.
Open The Lab →