Helium He , chemical element , inert gas of Group 18 noble gases of the periodic table. The boiling and freezing points of helium are lower than those of any other known substance. Helium was discovered in the gaseous atmosphere surrounding the Sun by the French astronomer Pierre Janssen , who detected a bright yellow line in the spectrum of the solar chromosphere during an eclipse in ; this line was initially assumed to represent the element sodium. That same year the English astronomer Joseph Norman Lockyer observed a yellow line in the solar spectrum that did not correspond to the known D 1 and D 2 lines of sodium, and so he named it the D 3 line. Ramsay obtained a sample of the uranium -bearing mineral cleveite, and, upon investigating the gas produced by heating the sample, he found that a unique bright yellow line in its spectrum matched that of the D 3 line observed in the spectrum of the Sun; the new element of helium was thus conclusively identified. In Ramsay and Frederick Soddy further determined that helium is a product of the spontaneous disintegration of radioactive substances. Helium constitutes about 23 percent of the mass of the universe and is thus second in abundance to hydrogen in the cosmos. Helium is concentrated in stars , where it is synthesized from hydrogen by nuclear fusion. The nucleus of every helium atom contains two protons , but, as is the case with all elements, isotopes of helium exist.
Reserves at Risk
Previous Element Hydrogen. Next Element Lithium. What's in a name? For the Greek god of the sun, Helios. Say what? Helium is pronounced as HEE-lee-em. Helium, the second most abundant element in the universe , was discovered on the sun before it was found on the earth. Sir Norman Lockyer, an English astronomer, realized that this line, with a wavelength of It was hypothesized that a new element on the sun was responsible for this mysterious yellow emission.
Flea on the Tail
All rights reserved. On August 18, , astronomers turned their telescopes toward a solar eclipse , not knowing they were about to expand the periodic table. Their goal was to discern the ingredients of solar prominences, the giant loops of glowing, electrified gas the sun occasionally belted out. When astronomers split the prominences' light into its components, they detected some colors they'd never seen before—the sign of an undiscovered element. This mysterious gas was helium, a substance so inert and whisper-light that it'd take scientists another 27 years to isolate it on terra firma. You may think of helium as the stuff in party balloons, or the gas that can make your voice squeaky. But helium has revealed itself to have an array of more practical uses, from essential equipment in science labs to common medical scanners and even scuba tanks.
It is a colorless, odorless, tasteless, non-toxic, inert , monatomic gas , the first in the noble gas group in the periodic table. Helium is the second lightest and second most abundant element in the observable universe hydrogen is the lightest and most abundant. Its abundance is similar to this in both the Sun and in Jupiter. This is due to the very high nuclear binding energy per nucleon of helium-4 , with respect to the next three elements after helium.