It's Elementary

Lets take just two elements, hydrogen and helium. They are the only elements in the first period, with only the two electron containing 1s shell. Hydrogen has one proton and one electron. Helium has two of each and a full 1s shell. Both elements are gases, lighter than air. Hydrogen is very reactive, it explosively reacts with the oxygen in the air in an attempt to lose that one electron.

Remember the Hindenburg?



It was a German passenger airship or blimp filled with hydrogen so it could fly. When landing in New Jersey in 1937 a fire started when it was connecting to its mooring tower and the ship exploded, burning up in just a few minutes. Although the exact cause of the fire is still unknown, the hydrogen certainly accelerated the rate at which the ship was destroyed.

Helium on the other hand is very stable and does not react with other atoms. Airships are now filled with helium and will not burn like the Hindenburg. Helium is so safe due to its stable electron shell that we use it to fill our party balloons.

Hydrogen and Helium are the two main elements on the Sun. Hydrogen atoms are fused together (nuclear fusion) to produce Helium atoms. This produces energy in the form of heat and light. It is this reaction that allows for the possibility of life on Earth. Without this heat from the Sun, our planet would be a frozen wasteland.