Amorphous form is a red-brown powder, while the crystalline form is a very reflective black/gray solid. m.p. (gray) 217 ºC; 423 ºF b.p. (gray) 684.9±1.0 ºC; 1264.8±1.8 ºF density (gray) 4.79, (vitreous) 4.28 g/cc; (gray) 299.03, (vitreous) 267.19 pound/cubic foot	memory peg
	1817 Jakob Berzelius, Sweden
	Σεληνη (Selènè) = the Moon (Greek)

Selenium was first identified in 1817 by the Swedish chemist Jakob Berzelius (1779-1848) (note). Berzelius and his colleague Johann Gottlieb Gahn (1745-1818) were studying a method of producing sulphuric acid in lead cameras when they observed residues of a substance with a very intense scent in the bottom of the camera. At first, they thought it was Tellurium. However, a more careful analysis revealed that there were no residues of this element, in spite of its identical properties. To this new substance was given the name Selenium, term that derives from the Greek Σεληνη [Selènè] (Moon). Since Klaproth had named Tellurium for the Earth, Berzelius thought it appropriate to name the sister element for the Earth's satellite:

In 1873 two English telegraph engineers, Willoughby Smith (1828-1891) and his assistant Joseph May experimented with Selenium and light. They noted that when selenium was exposed to light, its electrical resistance decreased. Thus was discovered the means to transform images into electric signals. Selenium became the basis for the manufacture of photoelectric cells, and the television.

In mythology, Selene resembles a young woman with an extremely white face who travels on a silver chariot drawn by two horses. She is often shown riding a horse or a bull. Selene is said to wear robes, carry a torch, and wear a half moon on her head. She was not one of the twelve great gods on Olympus, however she is the moon goddess. After her brother Helios completes his journey across the sky, she begins hers. Before Selene's journey across the night sky she bathes in the sea. She is known for her countless love affairs. The most famous of her loves is the shepherd Endymion. Encyclopedia Mythica.

← The goddess Diana (Selene) (Rome, Vatican Museums)

• Mary Elvira Weeks, Discovery of the Elements, comp. rev. by Heny M. Leicester (Easton, Pa.: Journal of Chemical Education, 1968), pp. 305-317.