Arsenic

Metalloid · atomic number 33

3374.9215956AsArsenicSolidMetalloid

Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. Arsenic is a metalloid.

Properties of Arsenic

Element category	Metalloid
Atomic number	33
Atomic mass	74.9215956 u
Phase at STP	Solid
Group	15
Period	4
Block	p
Electron configuration	[Ar] 3d10 4s2 4p3
Electrons per shell	2, 8, 18, 5
Electronegativity (Pauling)	2.18
Melting point	1090 K (817 °C)
Density	5.727 g/cm3
Discovered by	Bronze Age

← Germanium · Periodic table · Selenium → Se

About the metalloid group

In-between elements that behave as semiconductors: silicon, germanium and boron underpin electronics, glass and solar cells.

Data: Periodic-Table-JSON (CC BY-SA 3.0) · stored statically on our server. https://en.wikipedia.org/wiki/Arsenic

Explore by category — Periodic Table /unsur

⚛️ Full periodic table

All 118 chemical elements on one interactive, colour-coded table, each linking to a fact file and plain-language summary.

🧪 Reactive nonmetal

11 elements: Elements that readily gain or share electrons — the building blocks of water, air, living tissue and most organic chemistry.

🧪 Noble gas

6 elements: Full outer electron shells make these gases almost inert: they barely react, glow in discharge lamps and are used to create unreactive atmospheres.

🧪 Alkali metal

6 elements: Soft, wildly reactive metals of group 1 — they fizz in water and never occur pure in nature. Lithium, sodium, potassium and friends.

🧪 Alkaline earth metal

6 elements: Reactive group-2 metals a step calmer than the alkalis: magnesium, calcium and the structural and biological workhorses among them.

🧪 Transition metal

35 elements: The dense, strong, catalytic heart of the table — iron, copper, gold, titanium — responsible for most of metallurgy, jewellery and industry.

🧪 Post-transition metal

9 elements: Softer, lower-melting metals beside the transition block — aluminium, tin, lead — abundant in cans, foils, solders and pigments.

🧪 Metalloid

7 elements: In-between elements that behave as semiconductors: silicon, germanium and boron underpin electronics, glass and solar cells.

🧪 Lanthanide

15 elements: The rare-earth “inner transition” metals that give strong permanent magnets, screen phosphors and catalyst polish.

🧪 Actinide

15 elements: Mostly radioactive, heavy metals — several made only in reactors — whose fission powers nuclear energy and weapons.

🧪 Unknown properties

8 elements: Superheavy synthetic elements made atom-by-atom, existing for fractions of a second; their true chemistry is still unmeasured.