Although He is the second most abundant element in the universe, it is very rare on the earth. Why?

Helium (He) is a noble gas with the atomic number 2. It is an extremely light element, which means it has a very low density. Due to its light nature and its inability to react chemically with other elements (noble gas), helium does not form compounds, making it difficult to find it in combination with other elements.

Helium is the second most abundant element in the universe, just after hydrogen. The reason for its abundance in the universe is because it is formed as a byproduct during nuclear fusion, which occurs in the cores of stars. In this process, hydrogen atoms combine to create helium atoms, releasing energy in the form of heat and light.

Even though helium is abundant in the universe, it is very rare on Earth. There are a few key reasons for this: 1. Helium's light nature: Since helium is so light, it can easily escape Earth's gravitational pull and be lost to space. This means that helium in the Earth's atmosphere has a higher likelihood of leaving the planet when compared to heavier elements like oxygen and nitrogen. 2. Lack of production on Earth: On Earth, helium is produced through the radioactive decay of elements like uranium and thorium in the Earth's crust. The amount of helium generated through this process is relatively small compared to the amounts generated in stars.

As per the availability and formation of helium on Earth, it primarily accumulates in natural gas deposits. Extraction and purification of helium from natural gas are utilized for various requirements, including cooling in cryogenic applications, medical research, and lifting purposes, such as balloons and airships. However, due to its rarity and difficulty in obtaining, helium can be an expensive resource. In conclusion, helium's rarity on Earth can be attributed to its light nature, making it more likely to escape Earth's gravitational pull, and the limited production of helium through radioactive decay in the Earth's crust. These factors, combined with its abundance in the universe through nuclear fusion in stars, explain why helium is the second most abundant element in the universe but is considered rare on Earth.