n.<化>氦
Helium is a gas used in balloons.
氦是一种用于气球的气体.
Unlike helium - 4, it cannot be produced by radioactive decay.
与氦 - 4不同之处是, 氦-3不能由放射性衰变产生.
Helium is a very light gas.
氦是一种非常轻的气体。