Problem: What would you expect for the magnitude and direction of the bond dipoles in this series: BH4–, CH4, NH4+?

Molecular geometry can determine molecular polarity

• polar → has net dipole 

BH₄^–, CH₄, NH₄⁺→4 H atoms bonded to central atom

• AX₄ → tetrahedral → nonpolar → no net dipole moment