How do you get 3 different molecular shapes from a tetrahedral distribution of electrons?

Four groups of electrons around the central atom form a tetrahedral electron geometry with 109.5 degree bond angles.

Click to show the tetrahedaral distribution of electrons
When these four groups of electrons are bonded to four atoms, you also have a molecule with a tetrahedal molecular geometry with 109.5 degree bond angles.
Click to show the tetrahedral molecule.
When only three electron pairs are bonded atoms and the other is a lone pair, you have a molecule with a trigonal pyrimidal molecular geometry.
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When only two electron pairs are bonded atoms and the other two are lone pairs, you have a molecule with a bent molecular geometry.
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