Why is it important for scientists to use the international system of units

It is important for scientists to use the international system of units, because those all around the world are familiar with it, and so when scientists from different countries try to communicate with each other and tell of the scientific equations they know, the international system of units makes it easy to express small or large numbers, and so when it comes to scientific equations, it is easy to communicate with eachother on the numbers, which results in easier results.

The molecules contain like 54 of water 

No. an alpha particle is a pair of protons and a pair of neutrons, i.e. a helium