Chlorine an element

Chlorine an element in which the nucleus contains 17 protons. 

After the fumes had condensed on the cold surface of the tank, Courtois noticed a residue of dark purple, metallic-looking crystals. A sample of this made its way into the hands of French chemist Joseph Gay-Lussac. He d heard that Sir Humphrey Davy also had a sample, and he didn t want an Englishman to make a big discovery based on a Frenchman s shrewd observation, so he got to work. Gay-Lussac experimented feverishly and discovered that the purple material was a new element. He named it iode, from the Greek for violet. Davy suggested iodine, echoing chlorine, an element that iodine resembles. 

Most substances can be decomposed into two or more simpler substances. Water can be decomposed into hydrogen and oxygen. Sugar can be decomposed into carbon, hydrogen, and oxygen. Table salt is easily decomposed into sodium and chlorine. An element, however, cannot be decomposed into simpler substances by ordinary chemical changes. 

---