CH3 is not a stable molecule. It would have an unpaired electron on the carbon atom, making it a radical. However, if we consider the methyl radical (CH3•), which is a highly reactive species, its molecular geometry is trigonal planar.

Here's why:

* Carbon has 4 valence electrons.

* It forms 3 single bonds with hydrogen atoms, leaving one unpaired electron.

* The 3 bonds and the unpaired electron are arranged in a trigonal planar geometry to minimize electron repulsion.

The unpaired electron makes the methyl radical extremely reactive. It seeks to gain another electron to complete its octet.