Facts About Hydrogen and Helium

While they are the lightest of the elements and the sole occupants of the top period or row of the periodic table, hydrogen and helium have more differences than similarities. Although both are gases at room temperature, hydrogen is extremely reactive and forms thousands of compounds; as a member of the noble gases, helium is extremely stable and forms no compounds.

History

Helium was first discovered in a spectrograph of the sun taken during a solar eclipse.

Hydrogen (H), atomic number one, was produced for many years before it was determined to be a separate element. In fact, hydrogen gas was produced as early as 1671 by Robert Boyle but not recognized as a distinct element until 1766. Its name came from two Greek words hydros and genes, which mean "water forming." Helium, whose name comes from the Greek word for the sun helios, was first discovered on the sun and not on earth. Helium was first noticed in 1868, when French astronomer, Jules-César Janssen, discovered lines in a spectrograph of the sun which belonged to no known element. Helium was first found on earth in 1895 by Scottish scientist Sir William Ramsay.

Hydrogen

Hydrogen is the most abundant element in the universe.

The most abundant element in the universe, hydrogen is composed of one proton and one electron although its two isotopes, deuterium and tritium, also have neutrons. Although it is estimated that 90 percent of the universe is composed of hydrogen, its light weight and extreme reactivity insures that little if any pure hydrogen is found on earth. Instead, it is found through the decomposition of certain compounds, the electrolysis of water, and the reaction of certain compounds.

Helium

While hydrogen is abundant, helium (He), atomic number two, makes up less than .0005 percent of the Earth's atmosphere with much of it lost to space because of its light weight. Helium is composed of two protons, two neutrons, and two electrons, and is found in natural gas deposits. As a noble gas, it does not form any compounds, but is used with oxygen to create a nitrogen free atmosphere for scuba divers. It is also used to inflate a variety of balloons and is being used in the study of superconductivity of magnets. It is also used as a shield in arc welding.

Hydrogen vs. Helium

While hydrogen has also been used to inflate balloons and was the first choice to inflate early blimps for transatlantic trips, the crash of the German passenger air ship Hindenburg as it attempted to land in New Jersey in 1937 brought an end to its use for this purpose. Because helium is much safer (i.e. more stable) than hydrogen, helium is used in all situations where reactivity is not needed or desired.

Reactivity

Hydrogen is being looked as the next source for automobile fuel to lessen dependence on oil.

Because of its reactivity, hydrogen is located in the same column as the alkali earth metals. Because of the one electron that circles the nucleus, hydrogen readily forms ionic compounds by losing an electron or covalent bonds by sharing an electron. It is usually represented with the formula H2 to reflect its covalent bonds. It is one of the main components of fuels. And currently, attempts are being made to use pure hydrogen to power automobiles.

References

• Los Alamos National Laboratory's Chemistry Division: Hydrogen
• Jefferson Lab: It's Elelmental
• Web Elements: Hydrogen

Resources

• Chem Cool