Identifying radicals [ENDORSED]

[Nahelly Alfaro-2C]

I know that radical is an atom, molecule, or ion that has unpaired electron but I still have difficulty identifying the radical. Can someone explain how to identify a radical? For example, problem 3.55 part (B)-CH3

[Marisol Sanchez - 1E]

My TA told us that the easiest way to tell if a molecule is a radical is if it has an odd-numbered amount of valence electrons. If it has an even number of valence electrons then it would not be a radical. So you just have to add up how many electrons each atom has, take into consideration any charges, and then see if the number is even or odd.

[Daniel Cho Section 1H]

As an added bonus, when trying to draw the Lewis structure. When you see the odd number of valence electrons, my TA told me that when drawing the electrons, always start on the most electronegative atom since they are the atoms that want the electrons the most. Make sure to fill the atom until they complete the octet and then go on to fill in the rest of the electrons on the other element. For example, since NO is a radical 5+6=11 v.e. You would put the 6 electrons on oxygen first and then put the remaining 5 electrons on Nitrogen seeing that there is a radical on N.

I hope this helps. Please correct me in places where I might be wrong.

[Alma Flores 1D]

Also, after drawing the Lewis structure and finding the total amount of valence electrons, if there is a radical you will notice that the central atom does not complete its octet. For 3.55 part B, CH3 has 7 valence electrons. Carbon will form 3 bonds with the hydrogens and will have one lone pair electron. This lone pair electron makes it a radical.

[Brynne Keyser 1B]

A radical can easily be identified if it has an odd number of valence electrons, since electrons usually come in pairs