Total number of valence electrons in the molecule ${\mathrm{CH}}_3\mathrm{CHO}$ is

Total number of valence electrons in given molecule calculated as

${\mathrm{CH}}_3\mathrm{CHO}$

$2\times \mathrm{C}=2\times 4=8$

$4\times \mathrm{H}=4\times 1=4$

$1\times \mathrm{O}=1\times 6=6$

=18

Total valence electrons are 18.