valenceelectrons

Valence Electrons
Valence Electron Song: media type="file" key="Valence Electrons.mp3"


 * Websters Dictionary** defines a valence electron as   "an electron of an atom, located in the outermost shell (valence shell) of the atom, that can be transferred to or shared with another atom."

Basically, a "VE" is the electron is on the outside of an electron and thusly can be switched with other atoms. Valence Electrons are the electrons in an atom that are more likely to lost, gained or shared in the formation of chemical compounds.

Group Trends
In the periodic table, each group determines how many valence electrons is in each atom for that group. A chart is available below this text for reference. If you are having trouble remembering how many valence electrons there are in a certain group, just remember: Groups 1 and 2 have 1 and 2. 3-12 don't matter, and 13-18 is just the group number minus 10!
 * = Group Number ||= Number of Valence Electrons ||
 * Group 1 || 1 ||
 * Group 2 || 2 ||
 * Groups 3-12 || 1 or 2 ||
 * Group 13 || 3 ||
 * Group 14 || 4 ||
 * Group 15 || 5 ||
 * Group 16 || 6 ||
 * Group 17 || 7 ||
 * Group 18 || 8 (except He which has 2) ||

Period Trends
All of the atoms in a period have the same number of valence electrons as the period above or below it. This is because the number of valence electrons is determined by the groups and not periods. The only exception to this is Helium which is in group 18 which normally has 8 valence electrons but Helium only has 2.

Electron Configuration
If you look at the last two sublevels (ignoring the 1s//2// after H and He) in the electron configuration, you'll see that if you add the number of electrons together, it will form the number of valence electrons. See the chart below.

=Electronegativity= It is a chemical property of an atom which describes the ability of it to attract other electrons in the form of a covalent bond. Only the electrons in the valence band will join with other atoms though. Electronegativity can be described many ways but the most common is the Pauling Scale. This scale works by saying that Flourine has the highest electronegativity (4.0). The closer an element is to Flourine (on the periodic table) the higher its electronegativity is. See "On the Periodic Table".

How Electron Configuration Effects It
There is no correlation between Electronegativity in an atom and its electron configuration.

Period Trends
Generally, electronegativity increases from left to right in a period. There are a few exceptions as you can see in the chart. One of them is that Gallium and Germanium have a higher electronegativity than aluminum and silicon. The atomic radii of the atoms decreases so in turn the ionization energy increases and directly with that the electronegativity increases. The electrons on the left only have 1 or 2 electrons and would rather give them away them take more. This would give them a full outer energy level of 8. The elements on the right have a stronger desire to gain more electrons becausy they almost have a full valence band. This gives them a higher electronegativity.

Group Trends
As you go down the groups from top to bottom the electronegativity decreases. The electrons in the lower periods have a stronger desire to gain more electrons because they have to few. Once you get the higher periods they do not care as much to gain electrons since they have so many.

On the Periodic Table
Electronegativity ranges from 0 to 4.0 (on what is called the Pauling scale) with Florine at 4.0 and the elements further from it have lower electronegativity. This forms a diagonal arrow point from the bottom left of the periodic table to the top right (where Florine is). There are a few exceptions to this rule as you can see on the periodic table below.



=Electron Shielding Cartoon (Video)= media type="custom" key="2906649" In this video there are several symbols: The candles are the nucleus. The fireplace is all the protons/neutrons surrounding the nucleus. Alex is a valence electron. Brian is an electron in the energy level in between the nucleus and valence electron or "shielding electron". The heat from the fire is an attraction (positive charge) between the nucleus and other electrons (negative charge).

Because Alex (valence electron) was farther away from the candles (nucleus) than Brian (shielding electron), and Brian was in between Alex and the candles, he was blocking Alex from the heat (attraction of nucleus). Thus, he shields Alex from the heat.

QED

=Review Questions=

Knowledge

 * 1) In what way does the electronegativity move on a periodic table (to top left, to top right, to bottom left, to bottom right)?
 * 2) What energy level is a valence electron on?
 * 3) When are valence electrons exchanged?

Critical Thinking

 * 1) If you have Oxygen, Sulfur, and Copper. Which one of these has the highest electronegativity and why?

Calculation

 * 1) How many valence electrons do the following elements have?
 * 2) Flourine
 * 3) Phosphorous
 * 4) Helium
 * 5) Xenon
 * 6) Copper

=**Cites=

Our Science Book http://dl.clackamas.cc.or.us/ch104-06/valence_electrons.htm http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch8/index.php#electro http://www.colorado.edu/physics/2000/periodic_table/valence_electrons.html http://www.chemguide.co.uk/atoms/bonding/electroneg.html http://www.meta-synthesis.com/webbook/36_eneg/electroneg.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Electronegativity.html