Shielding

Authored by Ethan Bennis (Some original data by Mr. Williams!)
 * Electron Shielding**

The effective nuclear charge of an atom can have a large effect on its properties. If a single atom is orbiting around a nucleus (like in a Hydrogen atom), then we can measure the forces holding it around the nucleus without much difficulty. However, when there are multiple electrons, which is mostly the case, there are more forces at work. Electrons will be pulled towards the nucleus' positive charge, but also will be repelled by other the electrons' negative charge. (Opposite charges attract, like charges repel)

The electrons in an atom between its nucleus and the valence shell have a negative effect on its overall nuclear charge. Thus, the further away the valence electrons are from the nucleus, the less they are drawn to it, and thus are said to be more "shielded" from the core.

Shielding generally increases in a nice orderly fashion- simply across the periodic table. It does this for the following reasons: • An increase in the number of protons. • An increase in the number of electrons.

Electron shielding can be very roughly calculated by taking the charge of the nucleus (number of protons) minus the "shielding" electrons that are before the valence shell.

The knowledge of how these trends are affected by the effective nuclear charge can also be used to analyze such properties as atomic radius, melting/boiling points, electro negativity, and ionization energy. Additional information on the effective nuclear charge can be attained at our Effective Nuclear Charge page.

Sources: Our Chem book- [|Chemistry: The Central Science] and [|http://www.chembio.uoguelph.ca/educmat/atomdata/shield/shield.htm/]