How Does Helium Works?
The way how Helium works is the same as the Law of Buoyancy. Comparatively, if you stand in a pool of water 10 feet deep compared to the same stand of 10 feet in an open air, you are actually standing in a pool of air which is several miles deep.
Helium is a lot less dense than air. The difference in density is not as significant as it is between air and water, but of course it is significant. The weight of Helium in one liter is 0.1785 grams while the weight of air in one liter is an estimated 1.25 grams. Therefore, if you weigh a 1 liter bottle full of Helium, the weight will be less than 1 gram of a bottle full of air.
In this case however, the bottle will not float either in the air or in water because the bottle which weighs more than 1 gram is heavier than the Helium content. But in large volumes of Helium placed in lighter containers where its weight is heavier than its container, you can be sure that the container will float.
This is the reason why balloons are made in a standard size where Helium can be greater than their weight and they have to displace a large volume of air to float. Helium balloon is displacing an amount of air as it is with an empty bottle which is displacing an amount of water.
If the weight of Helium and the balloon is less than the air it displaces, absolutely, the balloon will float in the air. So, why is Helium lighter than the air?
Helium atoms have less weight than nitrogen atoms contained in the air. They contain less electrons, protons and neutrons than nitrogen atoms. Approximately, the weight of Helium atoms is 4 and nitrogen contained in the air is 14. That makes Helium lighter than air.
The same quantity of atoms in Helium and nitrogen fills the same amount of space in the air. The gases made of less dense atoms are lighter in weight.
What happens then if Helium is released in the air?
If you release a balloon filled with Helium in the air, it will go as far as it could go in the sky until it bursts out. Then, the Helium has no reason to stop; it just keeps going and finally leaks out into the space. Therefore, there is very small amount of Helium in the atmosphere at any given time because it moves away from the earth atmosphere.
The only available Helium in the air comes from Alpha particles emitted by radioactive decay. Helium is distilled out of natural gas to form the Helium that is used to fill in balloons. Just imagine if there is a big volume of Helium on the ground – it will cause a big explosion just like a hydrogen bomb.
In the past, hydrogen was used to fill balloons and it was quite popular then. Hydrogen has a weight of just 0.08988 grams per liter, much lighter than Helium. However, the danger posed by hydrogen is very high since it is highly flammable. A slightest spark can cause a big explosion that is why hydrogen balloons did not prosper.