The known isotopes of helium contain from one to six neutrons, so their mass numbers range from three to eight. The nucleus of every helium atom contains two protons, but, as is the case with all elements, isotopes of helium exist. Ordinary air contains about 5 parts per million of helium, and Earth’s crust is only about 8 parts per billion. Smaller supplies have been discovered in Algeria, Australia, Poland, Qatar, and Russia. Although helium occurs in Earth’s atmosphere only to the extent of 1 part in 200,000 (0.0005 percent) and small amounts occur in radioactive minerals, meteoric iron, and mineral springs, great volumes of helium are found as a component (up to 7.6 percent) in natural gases in the United States (especially in Texas, New Mexico, Kansas, Oklahoma, Arizona, and Utah). Helium is concentrated in stars, where it is synthesized from hydrogen by nuclear fusion. Helium constitutes about 23 percent of the mass of the universe and is thus second in abundance to hydrogen in the cosmos. In 1903 Ramsay and Frederick Soddy further determined that helium is a product of the spontaneous disintegration of radioactive substances.ġ18 Names and Symbols of the Periodic Table Quiz Abundance and isotopes 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. The British chemist Sir William Ramsay discovered the existence of helium on Earth in 1895. Lockyer concluded that the D 3 line was caused by an element in the Sun that was unknown on Earth he and the chemist Edward Frankland used the Greek word for sun, hēlios, in naming the element. 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. 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 1868 this line was initially assumed to represent the element sodium.

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