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Shapes of Molecules
Molecular shape depends on electron pairs around the central atom. Molecules and molecular
ions come in loads of different shapes and this shape depends on the number of pairs of
electrons in the outer shell of the central atom.
Electron pairs repel each other. Electrons are all negatively charged, so electron pairs will repel
each other as much as they can. Unfortunately, the type of electron pair affects how much it
repels other electron pairs. Lone pairs repel more than bonding pairs. So, the greatest angles
are between lone pairs of electrons, and bond angles between bonding pairs are often reduced
because they are pushed together by lone-pair repulsion.
Lone-pair/lone-pair bond angles are biggest
Lone-pair/bonding-pair bond angles are 2nd biggest
Bonding-pair/bonding pair bond angles are smallest