What is the second hardest material known?

Why hydrides of Germanium are known as _________

Tincal is ________

Bituminous is a common type of _________

Which of the following element exhibits + 3 Oxidation State only?

What is the colour of borax bead in the basic radical chromium test?

Is catenation possible in carbon?

Orthoboric acid is a weak monobasic Lewis acid.