How are elements that are heavier than hydrogen spread throughout the universe

Elements that are heavier than hydrogen are spread throughout the universe only during a supernova explosion. It is an explosion of the stars when the star reaches its death stage. When the star is alive, the gravity of its core squeezes lighter atoms like hydrogen to make heavier atoms like carbon and helium.

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%

well first you need the sample of the temperature and gas level. i couldnt write a hypothesis unless i had some data. i think temperature changes will effect volumes of gas because gas changed into a solid or liquid at specific temperatures.