What is the atomic number of sulphur?

When a metal $X$ is treated with cold water, it gives a basic salt $Y$ with molecular formula $XOH$ (molecular mass $= 40$) and liberates a gas $Z$ which easily catches fire. Identify $X$, $Y$, and $Z$, and write the chemical reaction involved.

In the $Bayer$ process,what is obtained when concentrated $NaOH$ is added to bauxite?

Bronze is an alloy of:

Which of the following acids is called 'the king of chemicals'?

Generally,non-metals are not lustrous. Which of the following non-metal is lustrous?