Helium
Hydrogen is the lightest element and has a greater lifting power than helium. However, toy balloons are filled with helium rather than hydrogen. Why?
Though hydrogen is twice as light as helium and also cheaper, the gas is not used in balloons because it is inflammable—it catches fire easily. Helium, the second-lightest element in the universe is an inert gas, which means it is non combustible, and safe to use in balloons whether they are toy balloons or scientific balloons. Balloons are the most visible form of helium use but the gas has an important role in scientific research and industry, and in its liquid form is essential in MRI machines where it cools the imaging magnets. Hydrogen, helium and lithium were the first three elements created at the formation of the universe, at the time of the Big Bang.
