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Natasha_4902
#1 Posted : Tuesday, August 04, 2020 3:41:29 AM
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Hi,

For radicals is the formal charge equation the same? In an altius practice exam it said that for the hydroxyl radical, the formal charge on the oxygen was -1 and on the hydrogen was +1. I am wondering how they got those numbers.

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INSTR_Katerina_102
#2 Posted : Tuesday, August 04, 2020 9:56:13 PM
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Hi Natasha,

Could you let me know the question so I can check? The formal charge rules should be consistent regardless of whether a molecule is a radical or not.

Thanks!

Katt
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Natasha_4902
#3 Posted : Wednesday, August 05, 2020 2:40:23 AM
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Hi,

The question is question #8 of the Altius full length 8 exam.

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INSTR_Katerina_102
#4 Posted : Wednesday, August 05, 2020 8:26:10 PM
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Hi Natasha,

The formal charge of both the atoms in the hydroxyl radical is zero.

However, this question is asking for the oxidation number, which does not necessarily equal the formal charge of each atom (but they should add up to the total charge of the molecule).

To calculate oxidation number, you imagine breaking a bond between two atoms, and having the electrons go to the more electronegative atom, in this case the oxygen.

From this point, the charge on the atoms is the oxidation number. For this case, because the O has 7 e- after splitting in this way, its oxidation number is -1. As the H has 0 electrons, its oxidation number is +1.

I have attached a diagram of this process.

https://alumniubcca-my.s...keEPxvtrmAMRqZg?e=0aOrAj

Please let me know if you need more clarification.

Katt
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