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Elements for Kids

Arsenic

The element arsenic

  • Symbol: As
  • Atomic Number: 33
  • Atomic Weight: 74.92
  • Classification: Metalloid
  • Phase at Room Temperature: Solid
  • Density: 5.727 grams per cm cubed
  • Melting Point: 817°C, 1503°F
  • Boiling Point (Sublimation Point): 614°C, 1137°F
  • Discovered by: Albertus Magnus in 1250
Arsenic is the third element in the fifteenth column of the periodic table. It is classified as a metalloid because it has some properties similar to a metal and others of a non-metal. Arsenic atoms have 33 electrons and 33 protons with 5 valence electrons in the outer shell.

Characteristics and Properties

Arsenic exists in a number of allotropes. Allotropes are different structures of the same element. Although they are made up of the same element, their different structures can have very different characteristics. For example, carbon has the allotropes graphite and diamond.

Arsenic's two most common allotropes are yellow and metallic gray. Gray arsenic is a brittle shiny solid. Yellow arsenic is soft and waxy. Yellow arsenic is reactive and very toxic. It converts to gray arsenic when exposed to light at room temperatures. Another allotrope is black arsenic.

How poisonous is arsenic?

Arsenic is perhaps most famous for its high toxicity. This means that it is very poisonous. Many of its compounds are poisonous as well. Too much arsenic can quickly kill a person and it has been used in assassinations throughout history. Also, exposure to small amounts of arsenic over time can cause many health issues. There are many laws on how arsenic should be handled and disposed of when used in industry.

Where is it found on Earth?

Arsenic is found in the Earth's crust. It can be found in its free form, but this is rare. Most arsenic exists in minerals such as realgar, mispickel (arsenopyrite), and orpiment. Arsenic for industrial use is generally produced as a byproduct from mining gold, silver, and copper.

How is arsenic used today?

Arsenic has been used in the past as an insecticide as well as a wood preservative. Because of environmental issues it is no longer used as an insecticide and is being phased out as a wood preservative in the United States. As a wood preservative, the compound copper arsenate helped to stop wood from rotting and also kept termites and other insects from destroying the wood.

Arsenic is combined with gallium to produce gallium arsenide for use in high speed electronics and optoelectronics. Other applications for arsenic include metal alloys and glass making.

How was it discovered?

Arsenic has been known about since ancient times as part of a compound with sulfur. It is thought that it was first isolated during the Middle Ages by German philosopher Albertus Magnus in 1250.

Where did arsenic get its name?

Arsenic may have gotten its name from the Greek word "arsenikon" which means "yellow pigment" or "arsenikos" which means "potent."

Isotopes

Arsenic occurs in nature in one stable isotope which is arsenic-75.

Interesting Facts about Arsenic

More on the Elements and the Periodic Table

Elements
Periodic Table

Alkali Metals
Lithium
Sodium
Potassium

Alkaline Earth Metals
Beryllium
Magnesium
Calcium
Radium

Transition Metals
Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Silver
Platinum
Gold
Mercury
 Post-transition Metals
Aluminum
Gallium
Tin
Lead

Metalloids
Boron
Silicon
Germanium
Arsenic

Nonmetals
Hydrogen
Carbon
Nitrogen
Oxygen
Phosphorus
Sulfur
 Halogens
Fluorine
Chlorine
Iodine

Noble Gases
Helium
Neon
Argon

Lanthanides and Actinides
Uranium
Plutonium

More Chemistry Subjects

Matter
Atom
Molecules
Isotopes
Solids, Liquids, Gases
Melting and Boiling
Chemical Bonding
Chemical Reactions
Radioactivity and Radiation
 Mixtures and Compounds
Naming Compounds
Mixtures
Separating Mixtures
Solutions
Acids and Bases
Crystals
Metals
Salts and Soaps
Water
 Other
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Science >> Chemistry for Kids >> Periodic Table


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