Why does methane have a tetrahedral shape even if it can have a square planar shape?
A methane molecule consists of Four Bond pairs (electrons participating in bonding) which repel each other. This repulsion increases the energy of the molecule, which is not favourable. So the molecule tends to reduce its energy by increasing the angular distance between each pair. In a square planar molecule, the angle between each bond pair is 90 degrees while for a tetrahedral shape, it is approximately 109 degrees. so a tetrahedral shape is preferred. Also, most square planar molecule are either dsp2 hybridised complexes or sp3d2 hybridised molecules with 2 lone pairs while sp3 hybridised molecules, like methane, exhibit a tetrahedral shape due to the above mentioned reason.
