Argon

Its symbol is Ar. It is the most abundant of the noble gases and the third most prevalent gas in the earth’s atmosphere. Argon comes from the Greek word “argos” meaning “inactive”. This is because argon does not easily react with other elements. This element was discovered in 1894 by the British Scientists Sir William Ramsay and Baron John William Strutt Rayleigh of Britain. Argon is colorless and odorless. Its uses are in light bulbs, arc welding, fluorescent light tubes, among others.

Arsenic

Its symbol is As. It comes from the word “ Arsenicos” or male. Arsenic was discovered by Albertus Magnus of Germany in 1250. The element is a steel gray, very brittle, crystalline, semi-metallic (metaloid) solid. It tarnishes in air, and when heated rapidly oxidizes to arsenous oxide which has a garlic odor. Arsenic is noted for being poisonous, however, some of its compounds are medicinal. It has been known since the ancient times. It is used for hardening shots, laser materials, poisons, insecticides, doping agents, among others.

Astatine

Its symbol is At. Astatine comes from the word Astatos or “unstable”. It was originally called alabamine. The element was first artificially prepared in 1940 at the University of California by bombarding bismuth with high-energy alpha particles. Astatine is the halogen which behaves most like a metal and that has only radioactive isotopes. Astatine is highly carcinogenic.

Barium

Barium is one of the alkaline-earth metals. Its symbol is Ba. It comes from the word “barys” or heavy or dense. The English scientist Sir Humphry Davy discovered it in 1808. It is a metallic element, soft and when pure is silvery white like lead. The metal oxidizes very easily and it reacts with water or alcohol. It is used in spark plugs, rubber, paint, glass, x-ray, rat poison, fireworks to name a few.