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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: transgalactic on January 24, 2009, 03:09:58 AM

Title: describing bond between elements..
Post by: transgalactic on January 24, 2009, 03:09:58 AM

regarding case B:
http://img525.imageshack.us/my.php?image=84419342em1.gif

before Br has 17 electrons
after the reaction each Br gets 1 electron
so each Br must have 18 electrons

but in the solution
they have only 8

its not 18
??

Title: Re: describing bond between elements..
Post by: Astrokel on January 24, 2009, 04:38:04 AM

Quote

before Br has 17 electrons

huh?

Title: Re: describing bond between elements..
Post by: transgalactic on January 24, 2009, 05:12:16 AM

Br=[Ar]3d^10 4s^2 4p^5

10+2+5=17

Title: Re: describing bond between elements..
Post by: Astrokel on January 28, 2009, 09:42:54 AM

Why do you include the 3d electrons? It doesn't mean 3d, 4s, 4p electrons are the valence electrons when written in this form.

Title: Re: describing bond between elements..
Post by: TheJoker on January 28, 2009, 06:58:24 PM

When it is written in this form though:

elemental Br=[Ar]3d^10 4s^2 4p^5

you can look at the highest energy level (in this case 4) and then get the valence electrons in these orbitals (in this case 7 valence electrons), that is why each bromine gets one electron, to have eight valence electrons and have a stable octet. That is why it shows eight valence and not 18