Helium is very useful in society, including specialized scientific experiments, medical procedures and even party balloons. Refer to the text above for a more detailed explanation of this image. "Big bang nucleosynthesis" explains the abundances of helium seen in the universe today. Figure 2 below demonstrates this process (the 74% of hydrogen and 26% of helium are their relative mass abundance, not the abundance compared to all other elements).įigure 2. The deuterons were then able to fuse into helium at a later time, explaining the abundance observed today.
#HELIUM VALENCE ELECTRONS FREE#
However, due to the stability of the deuteron (a neutron bound to a proton), this decay was thwarted, and neutrons were able to exist much longer than in their free state. When the universe expanded it cooled off, meaning that this recombination was no longer possible, and neutrons began to decay. When the universe was dense and hot, protons and neutrons were able to exist in the same abundance (first section of Figure 2): this is because neutrons naturally beta decay into a proton and electron, however the high temperature allowed for the recombination of these into a neutron. The large abundances of helium found in the universe is evidence for the Big Bang theory. Therefore there are no known compounds of helium even in the laboratory people have never been able to get helium chemically react with anything. Įlemental helium does not chemically bond with other elements because it is inert, meaning its valence shell is completely full.
When this nucleus captures two electrons, it becomes elemental helium. Some elements go through alpha decay in which they emit an alpha particle, which is merely a helium nucleus. Helium is found naturally on Earth due to the radioactive decay of elements trapped underground (often in natural gas mines in the United States). Some properties of helium include: Atomic weight Because of this, it was suitably named helium after the Greek god of the Sun, Helios. Helium was discovered in the Sun before it was found on Earth, when astronomers were analyzing a solar eclipse in 1868. Helium is the 2 nd element on the periodic table, and it is the 2 nd most abundant element in the universe making up 23% of the total mass of all elements (some sources go as high as 25%). Helium with atomic number of 2 and atomic weight of 4.002602.
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