Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Cicada on March 17, 2007, 04:23:03 PM
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Hello, heres my question:
a)write a ground state electron configuration of for the arsenic atom
b)give a possible set of quantum numbers for each of the three outermost electrons of the arsenic atom
i know how to get the ground state, but i have no idea how to get the quantum number for each of the three electrons. I search google also, all i've found is articles regarding the ground state. At this point I am 100% stuck. thanks for *delete me*
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There are four quantum number: n, l, ml, and ms
n is the principle quantum number. It specifies the energy level of the electron. This can be any natural number (1,2,3,...)
l is the azimuthal quantum number. It specifies the type of orbital (s, p, d, f, etc.). l ranges from 0 to n-1.
ml is the magnetic quantum number, it specifies the orientation of your orbital (e.g. px v, py v. pz. ml ranges from -l to l.
ms is the spin quantum number. It specifies the spin of the electron (±1/2).
For more information see your chemistry text or wikipedia (the article isn't too well written though):
http://en.wikipedia.org/wiki/Quantum_number
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Alrightie. Which are the three outermost electrons? (What's the electron configuration of arsenic? You're looking for the last three electrons listed.)
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okay, for arsenic its this: 3d104s24p3, but thats the ground state, and the quantum numbers, from what i understand are distinct, so how can there be more than one configuration? I already read the wikipedia article, it didnt give me any help.
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So, the three outermost electrons are the three electron in the 4p orbital. Here you can already tell two of the quantum numbers, since the 4 denotes that n=4 and the p denotes that l = 1 (s orbitals have l=0, p means l=1, d means l=3, and f means l=4). Now, all you have to do is figure out the ml and ms values for these electrons. Remember that there are three distinct p orbitals, each with a different value of ml.
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okay, thanks, but there are 4 "variables" there, n,l,ml and ms, i thought there were only 3 quantum numbers?
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oh, i see, it because these are describing electrons, which can go in to direction in the same orbital, thanks again.
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so three possible quantum numbers for the outermost electrons could be:
n=4,l=1,ml=-1,ms=1/2
n=4,l=1,ml=0,ms=1/2
n=4,l=1,ml=+1,ms=1/2
... is this right?
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Yup, this is a correct possibility. You correctly remembered that each p orbital will have one electron each and that all electrons will have the same spin. The other correct possibility would be:
n=4,l=1,ml=-1,ms=-1/2
n=4,l=1,ml=0,ms=-1/2
n=4,l=1,ml=+1,ms=-1/2