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VSEPR Theory

VSEPR Theory. Ben Jahncke, Liam Barro and Kyle Murphy. What is VSEPR?. VSEPR stands for Valence Shell Electron Pair Repulsion.

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VSEPR Theory

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  1. VSEPR Theory • Ben Jahncke, Liam Barro and Kyle Murphy

  2. What is VSEPR? • VSEPR stands for Valence Shell Electron Pair Repulsion. • It states that groups of electrons in the valence shell of an atom repel each other and will position themselves in the valence shell so that they are as far apart as possible. • The VSEPR theory is used to accurately predict the shape of atoms invisible to the naked eye.

  3. Why does it work? • The VSEPR theory works upon the fact that all electrons in the valence shell of an atom fall into two electron domains. • The electrons in the bonding domain of an atom’s valence shell are used in bonding with other atoms. • The rest of these electrons organize themselves into lone pairs or simply remain single in the case of atoms with an odd number of valence electrons.

  4. Lewis structures • The bonding electrons in an atom take up a certain amount of space, thereby spreading all of the electrons in the valence shell. • Lone pairs create their own poles, which causes other electrons to be forced away. • These effects are best represented in a lewis dot diagram.

  5. These are simple examples of how the valence shell electrons of an atom effect the shape of said atom.

  6. Categorizing • The different VSEPR shapes are organized according to their steric number. • A compound’s steric number its the number of atoms o lone pairs situated around the compounds central atom. • For instance, BeCl2 has a steric number of two, because beryllium only has two atoms of chloride sharing it’s electrons, and has no lone pairs.

  7. Types of Shapes • There are many different types of shapes in the VSEPR theory, with some appearing to repeat, due to the presence of lone pairs. • These general shapes remain constant throughout the world of chemistry, with only slight variations in some of the angles.

  8. Common Shapes These are examples of many of the common VSEPR shapes known today. Notice that they are sometimes similar, with only a small variation in their respective angle sizes.

  9. The effect of lone pairs • Lone pairs tend to create larger domains, which in turn push other domains further away. • This effect is most noticeable in the difference between the bent shape and trigonal planar shape. Their sole difference is that instead of having three bonding domains like trigonal planar, the bent shape has a lone pair, which forces it’s other two domains further away. This creates an angle measured at less than 120 degrees, compared to trigonal planar’s three angles of exactly 120 degrees each.

  10. Bonding Pairs vs. Nonbonding pairs • As shown in this image, nonbonding domains are bigger than bonding domains. This is because there aren’t two electrons shared equally, resulting in a larger, uneven size in nonbonding domains.

  11. Conclusion • As shown before, the Valence Shell Electron Pair Repulsion theory is an important part of chemistry, as it’s rules are needed in order to understand the minute mechanics that take place on the molecular scale. This theory, first presented in 1940, has helped chemists around the world gain understanding on atoms and the role they play in our changing world.

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