The isoelectronic molecules CH4, NH3, and H20 (Figure 3-10) illustrate the effect of
lone pairs on molecular shape. Methane has four identical bonds between carbon and
each of the hydrogens. When the four pairs of electrons are arranged as far from each
other as possible, the result is the familiar tetrahedral shape. The tetrahedron, with all
H- C - H angles measuring 109.S0, has four identical bonds.