Question

Question #179ac

Answer 1

Iodine would have a standard electron configuration of

`1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^10 5p^5`

The noble gas in the row above iodine is krypton.

We can replace `1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6` with the symbol [Kr] and rewrite the noble gas configuration of iodine as

`[Kr] 5s^2 4d^10 5p^5`

I hope this was helpful.
SMARTER TEACHER

Answer 2

The full electron structure of iodine is :

`!s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(10)4s^(2)4p^(6)4d^(10)5s^(2)5p^(5)`

The noble gas Krypton has the electron configuration:

`1s^(2)2^(2)2p^(6)3s^(2)3p^(6)3d^(10)4s^(2)4p^(6)`

We refer to this as the "Noble Gas Core" which we can write as :

`[Kr]`

So now we can write the electron configuration as :

`[Kr] 4d^(10)5s^(2)5p^(5)`

You will note that iodine has 7 valence electrons in the outermost n = 5 energy level, `4d` being lower in energy than `5s`. These electrons define the chemistry of iodine which can use some, or all of them in chemical reactions with oxidation states ranging from -1 to +7.