Three-bonded atoms

The central phosphorus atom has one unshared pair and three bonded atoms. The molecule is of type AX3E it should be a trigonal pyramid (like NH3) with a bond angle somewhat less than 109.5° (actually, 104°). 

The shape around this carbon atom is trigonal planar. The molecule lies flat in one plane around the central carbon atom, with the three bonded atoms spread out, as if to touch the corners of a triangle. 

Single Pair of bonded Three bonded Atom in solid... 

A carbon with three bonded atoms is sp2-hybridized, trigonal, and has approximately 120° bond angles. There are three new sp2-hybrid orbitals directed to the corners of a triangle these form sigma bonds with other atoms. The remaining p-orbital overlaps with a parallel p-orbital of an adjacent, sigma bonded atom to form a pi-bond and complete the double bond. 

Three Electron Pairs, Three Bonded Atoms... 

Because N03 has three bonded atoms, it has a trigonal planar shape. 

The NH3 molecule has a tetrahedral electron geometry with three bonded atoms, which gives it a trigonal pyramidal shape. Thus, a NH3 molecule is polar because the individual N—H dipoles do not cancel. 

A central atom with four electron groups and three bonded atoms has a trigonal pyramidal shape. 

Answer From its electron-dot formula, we see that ASCI3 has four electron groups with three bonded atoms. 

In NF3, the central atom N has three bonded atoms and one lone pair of electrons, which gives NF3 a trigonal pyramidal shape. 

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