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ChemWiki: The Dynamic Chemistry E-textbook > Inorganic Chemistry > Descriptive Chemistry > Main Group Elements > Group 18: The Noble Gases > Chemistry of Helium > The Helium Atom

The Helium Atom

Since it was discovered, Helium, was the lightest element in the noble gases.  Even though it shares many common characteristics with other elements in the noble gases family, it also has many of its own unique traits. It is a gas that is colorless, tasteless, odorless, and non toxic. In the following article, we will explore more about Helium by understanding this element's origin, structures, physical properties, chemical properties, etc.

 

Atomic Mass

4.0026 g/mol

# Protons

2

# Neutrons

2

# Electrons

2

Electron Configuration

1s2

 

Introduction

Helium was discovered by Pierre Janssen and J. Norman Lockyer in 1868 and was found as a part of the sun's chromosphere.  The word helium or helios in Greek meaning sun. When Janssen studied the sun Lockyer found a line that was bright yellow and he thought it was some kind of hydrogen.  Later in the studies, both Janssen and Lockyer became convinced that they had just discovered a new element. 

After hydrogen, helium is the second simplest element of the periodic table and is part of the noble gases.  It is also the second most abundant element after hydrogen.

Origin on Earth

Many terrestrial helium are natural decay of alpha emitting radioactive minerals.  The earth crust only produces .5 cubic feet of helium per year and this is counted for the total amount of reserved helium and continuing loss to the atmosphere. 

 

Physical Properties

Because helium is a noble gas, some of the common physical characteristics are very low reactivity, completely filled outer levels, and are the smallest in size among their period.  Helium is special because it is the only element that doesn't solidify through a reduction solely in temperature, but it also requires an increase in pressure.  Helium is a colorless, odorless, non-toxic gas.

 

Boiling Point @ 1atm

4.216 K

Melting Point @ 1atm

1.0 K

Critical Temp

5.2 K

Critical Pressure

2.26 atm

Atomic diameter

2.56 A

Heat capacity

4.968 cal/K/g mole

Latent heat of vaporization

4.9 cal/g

Latent heat of fusion

1.0 cal/g

 

  • The data above is collected from the Macmillan Encyclopedia of Chemistry

Spectral lines of Helium

 

Chemical Properties

Helium has the valance of zero which means it will not be easily combine with othr element.  At extreme condition, such as extremely high temp, lower pressure..etc. the combination with other elements and helium has been observed. Helium has a low boiling point, low melting point, low  density, low solubility, and high thermal conductivity (compared to other noble gases).

Helium is part of the group of noble gases, which are also referred to as the "inert" gases, because of their inability to form chemical compounds with other elements.   

Helium with charges ( blue=protons, red=neutrons, minus signs=electrons)     

 

References

  1. Lagowski, J. J. Macmillan Encyclopedia of Chemistry. New York: Macmillan Reference USA, 1997. Print.
  2. McGraw-Hill Concise Encyclopedia Of Chemistry by Mcgraw-hill. Flipkart Books.  Ed. Sybil P. Parker. 1 July 2004. 

Problems

Be careful not to copy from existing textbooks. Originality is rewarded. Make up some practice problems for the future readers. Five original with varying difficulty questions (and answers) are ideal.

  1. When was Helium first discovered?

Answer: 1868

 

  1. Which element that is most closely related to helium?

Answer: hydrogen

 

  1. Does helium want to form with other elements and why?

Answer: No, because it has zero valance electron and stable as it is by itself

 

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Last Modified
10:17, 2 Oct 2013

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