posted by Britt .
The electron pairs in a molecule of NH3 form a tetrahedron. Why does the NH3 molecule have a trigonal pyramidal shape rather than a tetrahedral shape? Explain your answer.
This seems obvious to me and I don't know that there is much explaining possible. If the electrons and H atoms form a tetrahedron and you take away the top part of the tetrahedron, what's left?