As long as the helium plus the balloon is lighter than the air it displaces, the balloon will float in the air. Most of us feel comfortable with the idea of something floating in see that happen every day. In fact, people themselves float in water, so we have a way of directly experiencing water flotation.
· Since helium is much less massive than nitrogen and oxygen in the air, helium balloons float. However, the smaller size also explains why helium balloons deflate so quickly. The helium atoms are very tiny — so tiny the random motion of the atoms eventually lets them find their way through the material of the balloon through a process called diffusion .