Question

What has the smallest, lightest atoms of all the elements and is colorless, odorless, tasteless and nontoxic, but highly flammable in its pure state?

Answer 1

hydrogen

Hydrogen has the smallest, lightest atoms of all elements. Pure hydrogen is a colorless, odorless, tasteless gas that is nontoxic but highly flammable. Hydrogen gas exists mainly as diatomic  two-atom  molecules  H 2  , as shown in the diagram on the right. Hydrogen is the most abundant element in the universe and the third most abundant element on Earth, occurring mainly in compounds such as water.