There are six (6) bonding electrons are in the lewis structure of carbon monoxide (CO). In Lewis structure, there are ten (10) valence electrons of Carbon monoxide (CO). For lewis structure we need a triple bond between carbon and oxygen, so when electrons made a triple bond it means there is six bonding electrons in lewis structure of carbon monoxide.
The Lewis structure represents the valence electrons at the atoms, which ones are shared and the lone pairs. Carbon is at group 4 at the periodic table, and so has 4 electrons in the valence shell; oxygen is at group 6, and so has 6 electrons at the valence shell.
That compound is an exception of the octet rule. A triple bond is done between the atoms, and so, 3 electrons of carbon are shared and 3 electrons of oxygen are shared. Thus, there are 6 bonding electrons, as shown below in red.
