A colourless, toxic gas with the characteristic odour of rotten eggs. It occurs in certain mineral waters and spring waters.
A reddish-brown toxic gas, very reactive due to its unpaired electron.
The compound of hydrogen and oxygen. Colourless, odourless liquid; heavier than water.
A colourless, heavier-than-air gas with a pungent odour.
One of the allotropes of phosphorus.
Colourless, odourless gas, highly toxic to humans and animals in high concentration.