Education
- Double And Triple Bonds In Vsepr Theory
Molecular geometry is determined by possible locations of an electron in a valence shell, not by how many how many pairs of valence electrons are present. To see how the model works for a molecule with double bonds, consider...
- Exceptions To Vsepr Theory
Valence Shell Electron Pair Repulsion theory does not always predict the correct geometry of molecules. Examples of exceptions include: transition metal molecules (e.g., CrO3 is trigonal bipyramidal, TiCl4 is tetrahedral)odd-electron molecules (CH3 is...
- Predicting The Shapes Of Molecules
There is no direct relationship between the formula of a compound and the shape of its molecules. The shapes of these molecules can be predicted from their Lewis structures, however, with a model developed about 30 years ago, known as the valence-shellelectron-pair...
- Concepts Of Acids And Bases
Acids and bases have been given several concepts so that we can recognize them.Mainly Three concepts have been given.They are: 1)Arrhenius concept =>This concept states that,"A acid is a species which gives [H^+] ion in an aqueous solution and base...
- Discovery Of Protons
Protons are subatomic particles that, with neutrons and electrons, are the principal constituents of atoms. Protons are positively charged atoms that reside in the nucleus of an atom. These protons add the overall positive charge of a molecule. The mass...
Education
VSEPR Theory
Valence Shell Electron Pair Repulsion (VSPER) theory is used to predict the geometric shape of the molecules based on the electron repulsive force. There are some limitation to VSEPR.
Introduction
The shapes of the molecules is determined mainly by the electrons surrounding the central atom. Therefore, VSEPR theory gives simple directions on how to predict the shape of the molecules. The VSEPR model combines the original ideas of Sidwick and Powell and further development of Nyholm and Gillespie.
How VSEPR works
In a molecule EXn, the valence shell electron pair around the central atom E and the E-X single bonds are very important due to the repulsion in which determine the shape of the molecule. The repulsions decrease in order of: lone pair-lone pair, lone pair-bonding pair, bonding pair-bonding pair. At the same time, the repulsion would decrease in order of: triple bond-single bond, double bond-single bond, and single bond-single bond if the central atom E has multiple bonds. The difference between the electronegativities of E and X also determine the repulsive force between the bonding pairs. If electron-electron repulsive force is less, then more electron density is drawn away from the central atom E.
Shape determination:
VSEPR model works better for simple halides of the p-block elements but can also be used with other substituents. It does not take steric factors, size of the substituents into account. Therefore, the shape of the molecules are arranged so that the energy is minimized. For example:
- BeCl2 has minimum energy when it is a linear molecule.
- BCl3 takes the shape of trigonal planar.
Lone pair electrons are also taken into account. When lone pair electrons are present, the "parent structure" are used as a guideline for determining the shape..
- Double And Triple Bonds In Vsepr Theory
Molecular geometry is determined by possible locations of an electron in a valence shell, not by how many how many pairs of valence electrons are present. To see how the model works for a molecule with double bonds, consider...
- Exceptions To Vsepr Theory
Valence Shell Electron Pair Repulsion theory does not always predict the correct geometry of molecules. Examples of exceptions include: transition metal molecules (e.g., CrO3 is trigonal bipyramidal, TiCl4 is tetrahedral)odd-electron molecules (CH3 is...
- Predicting The Shapes Of Molecules
There is no direct relationship between the formula of a compound and the shape of its molecules. The shapes of these molecules can be predicted from their Lewis structures, however, with a model developed about 30 years ago, known as the valence-shellelectron-pair...
- Concepts Of Acids And Bases
Acids and bases have been given several concepts so that we can recognize them.Mainly Three concepts have been given.They are: 1)Arrhenius concept =>This concept states that,"A acid is a species which gives [H^+] ion in an aqueous solution and base...
- Discovery Of Protons
Protons are subatomic particles that, with neutrons and electrons, are the principal constituents of atoms. Protons are positively charged atoms that reside in the nucleus of an atom. These protons add the overall positive charge of a molecule. The mass...