Oxygen Free Radical Reactivity

[sexycani]

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What makes the O2 radical so reactive is:

A) Gain 2 electrons to fill its octet
B) Gain 1 electron to fill its octet
C) Lose 1 electron to fill its octet

I put C because in the lewis structure for O2 radical, there are 13e- and losing one will let the molecule have a stable octet around both oxygens...

the correct answer is B. Why?

(Btw, this question is #31 on PS from TBR CBT #5)

 

[LeoGer]

What makes the O2 radical so reactive is:

A) Gain 2 electrons to fill its octet
B) Gain 1 electron to fill its octet
C) Lose 1 electron to fill its octet

I put C because in the lewis structure for O2 radical, there are 13e- and losing one will let the molecule have a stable octet around both oxygens...

the correct answer is B. Why?

(Btw, this question is #31 on PS from TBR CBT #5)

An O2 radical has lost, not gained, an electron to become a radical. Now follow your same reasoning.

 

[sexycani]

ah! thanks for that
but how did you immediately know that it has lost an electron versus gained? i mean, radicals can form either way, right?

 

[flodhi1]

ah! thanks for that
but how did you immediately know that it has lost an electron versus gained? i mean, radicals can form either way, right?

You should look at the periodic table trends. When calculating or in this situation evaluating MCAT type questions try to keep a BROAD mind. Oxygen is towards the top and right side of the periodic table what does that tell you? It has a high electronegativity thus it will donate an electron not accept it. It's similar to other electronegative/ nucleophillic elements such as Flourine. They are not like metals they don't accept electrons like metals they tend to donate electrons. You can also reach the same conclusion when considering the fact that Flourine and Oxygen can be Lewis bases. They "donate" electrons thus to form a radical Oxygen would lose an electron. This is just a simple way of how I try to make sense out of things it might work for you or it might not. Regardless good luck!

 

[Rabolisk]

You should look at the periodic table trends. When calculating or in this situation evaluating MCAT type questions try to keep a BROAD mind. Oxygen is towards the top and right side of the periodic table what does that tell you? It has a high electronegativity thus it will donate an electron not accept it. It's similar to other electronegative/ nucleophillic elements such as Flourine. They are not like metals they don't accept electrons like metals they tend to donate electrons. You can also reach the same conclusion when considering the fact that Flourine and Oxygen can be Lewis bases. They "donate" electrons thus to form a radical Oxygen would lose an electron. This is just a simple way of how I try to make sense out of things it might work for you or it might not. Regardless good luck!

This is wrong or misleading for many reasons. High electronegativity has nothing to do with whether something will "donate" or "accept" electrons in the strictest sense. A highly electronegative atom will attract more of the electron density in a molecule. For example, in H2O, the electron density will shift towards oxygen, creating a partially negative end at the O. If anything, highly electronegative atoms will tend to ACCEPT electrons.

Also, nonmetals tend to accept electrons and form anions, and metals tend to lose electrons and form cations. You have this backwards. To be sure, it is possible for an oxygen-containing compound to act as a Lewis base or a nucleophile (e.g. OH-), but that's not what we are talking about here. Also, acting as a nucleophile is entirely different than acting as a reducing agent (donating an electron).

 

[flodhi1]

This is wrong or misleading for many reasons. High electronegativity has nothing to do with whether something will "donate" or "accept" electrons in the strictest sense. A highly electronegative atom will attract more of the electron density in a molecule. For example, in H2O, the electron density will shift towards oxygen, creating a partially negative end at the O. If anything, highly electronegative atoms will tend to ACCEPT electrons.

Also, nonmetals tend to accept electrons and form anions, and metals tend to lose electrons and form cations. You have this backwards. To be sure, it is possible for an oxygen-containing compound to act as a Lewis base or a nucleophile (e.g. OH-), but that's not what we are talking about here. Also, acting as a nucleophile is entirely different than acting as a reducing agent (donating an electron).

Thanks for the clarification I got it mixed up!