# Are alkyl groups and radicals the same? For example aldehydes R-CHO.

$A l k y l$ groups and $r a \mathrm{di} c a l s$ are not the same.
In its modern meaning, a $r a \mathrm{di} c a l$ is an atom, molecule, or ion that has unpaired valence electrons.
In this sense, an $a l k y l$ group is not a $r a \mathrm{di} c a l$ because all its electrons occur in pairs.
A $r a \mathrm{di} c a l$ was once defined as a group of atoms that took part in chemical reactions as a single unit.
According to that older definition, $a l k y l$ groups were $r a \mathrm{di} c a l s$. The functional groups like $a l \mathrm{de} h y \mathrm{de}$ groups made the molecule reactive. But the $a l k y l$ groups stayed together as a unit.