What is the stability order of various alkyl free radicals ? Why

Explanation

The stability order of alkyl free radicals is:
`underset(3^(0))((CH_(3))_(3) overset(.)(C ) gt (CH_(3))_(2)) underset(2^(0))overset(.)(C) H gt CH_(3) underset(1^(0))overset(.)(C )H_(2) gt overset(.)CH_(3)`
More the number of hyperconjugative structures, the greater is the stability. Tertiary butyl free radical has 9, isopropyl free radical has 6, ethyl free radical has 3 and methyl free radical has no hyperconjugative structures.