Era of discovery: Element classification (1850–1899)
Over 20 elements, including many heavy ones and also those of the rare earths, could be discovered by the end of the 19th century, so that almost all naturally occurring elements were known around 1900.
9F
Fluorinevery pale yellow (gas); bright yellow (liquid); alpha is opaque, beta is transparent (solid)
59Pr
Praseodymiumgrayish white
64Gd
Gadoliniumsilvery white
66Dy
Dysprosiumsilbrig weiß