Noble Gases

Examples of Noble Gases in the following topics:

• The Noble Gases (Group 18)

  • The noble gases are a group of chemical elements that make up Group 18 on the periodic table.
  • The properties of the noble gases can be well explained by modern theories of atomic structure.
  • Noble gases have the largest ionization potential among the elements of each period.
  • Under the correct conditions, brightly lit and colorful signs can be made using noble gases.
  • "Neon Lights" is the common term, but any of the noble gases can be used.

• Writing Lewis Symbols for Atoms

  • These are all gaseous under normal conditions of temperature and pressure, and are called 'noble gases.'
  • The noble gases represent elements of such stability that they are not chemically reactive, so they can be called inert.
  • The significance in understanding the nature of the stability of noble gases is that it guides us in predicting how other elements will react in order to achieve the same electronic configuration as the noble gases by having a full valence level.
  • Helium is one of the noble gases and contains a full valence shell.
  • Unlike the other noble gases in Group 8, Helium only contains two valence electrons.

• Substances that Exist as Gases

  • Gases behave most ideally at high temperatures and low pressures.
  • The group VIII elements (helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn)) exist as monatomic gases at standard temperature and pressure (STP) and are called the noble gases.
  • These gases, when grouped together with the monatomic noble gases are called "elemental gases. "
  • Note that unlike solids, gases do not follow a rigidly patterned structure; at a microscopic level, gases are always moving and rearranging themselves.
  • Gases have no definite shape or volume.

• Internal Energy of an Ideal Gas

  • In ideal gases, there is no inter-particle interaction.
  • Noble gases (He, Ne, etc.) are typical examples.
  • Note that there are three degrees of freedom in monatomic gases: translation in x, y and z directions.
  • Therefore, the internal energy for diatomic gases is U=52NkTU = \frac{5}{2}NkT.
  • Helium, like other noble gases, is a monatomic gas, which often can be described by the ideal gas law.

• General Trends in Chemical Properties

  • The main body of the table is an 18 by 7 grid, and elements with the same number of valence electrons are kept together in groups (columns), such as the halogens and the noble gases.
  • Moving left to right across a period, from the alkali metals to the noble gases, atomic radius usually decreases.
  • Electron affinity also shows a slight trend across a period: metals (the left side of a period) generally have a lower electron affinity than nonmetals (the right side of a period), with the exception of the noble gases which have an electron affinity of zero.

• Sulfur Compounds

  • Sulfur forms stable compounds with most elements except the noble gases.
  • Sulfur forms stable compounds with all elements except the noble gases.

• Ionic Bonding and Electron Transfer

  • This exchange results in a more stable, noble gas electronic configuration for both atoms involved.
  • Both types result in the stable electronic states associated with the noble gases.

• Introduction to Lewis Structures for Covalent Molecules

  • Noble gases like He, Ne, Ar, Kr, etc., are stable because their valence level is filled with as many electrons as possible.
  • Eight electrons fill the valence level for all noble gases, except helium, which has two electrons in its full valence level.
  • Other elements in the periodic table react to form bonds in which valence electrons are exchanged or shared in order to achieve a valence level which is filled, just like in the noble gases.
  • Hydrogen can become stable if it achieves a full valence level like the noble gas that is closest to it in the periodic table, helium (He).

• Atomic Radius

  • Radii generally decrease from left to right along each period (row) of the table, from the alkali metals to the noble gases; radii increase down each group (column).
  • The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period.
  • In a noble gas, the outermost shell is completely filled.

• Standard Entropy

  • For the noble gases, this is a direct reflection of the principle that translational quantum states are more closely packed in heavier molecules, allowing them to be occupied.
  • Gases, which serve as efficient vehicles for spreading thermal energy over a large volume of space, have much higher entropies than condensed phases.