The Russian word for copper is медь. Just as in English it is mostly used in the singular. It is a feminine third-declension noun:
Some sample sentences:
В США медь добывают больше всего в Аризоне.
In… more »
The Russian word for mercury, the element, is ртуть, which is a feminine third-declension noun. The word mostly occurs in the singular:
Image from Wikipedia
The place most of us used to encounter… more »
Водород is the Russian word for hydrogen. The English word is made up of Greek roots where ὑδρο- (hydro-) means ‘water’ and γεν- (gen-) means ‘‘bring forth/become,” thus hydrogen means “the substance that forms water.” Notice that the Russian word is… more »