Posted in P2 SBI4U Biology

SBI4U VSEPR: The Shape of Things

VSEPR – Valence Shell Electron Pair Repulsion Theory

This is used to determine the shape around an atom based on how it is bonded to other atoms.

bonding pair – a pair of electrons involved in a covalent bond, like the bond that holds hydrogen to oxygen in water.

lone pair – a pair of electrons around an atom that is not involved in bonding. Oxygen has two lone pairs around it no matter what. Nitrogen always has one lone pair around it in the biological molecules we will be exploring.

Click here and download the 3D model kit to practice VSEPR shapes.  You may have to update or download Java to run the program.

  • electron pairs repel each other in 3D space so repulsion is minimized
  • lone pairs are more repulsive than bonding pairs due to the absence of a nucleus
  • double and triple bonds are treated as a single bonding pair
  • only bonding pairs are used to declare the shape of the molecule around the central atom, but lone pairs may have an influence on this shape