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# I find myself doubting myself. - Chemistry Watch

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1. The principle quantum number:

Lowest energy electron of Krypton, it's quantum number would be 1, surely?
Highest energy of lithium would be 2?

Gah I hate doubting myself like this.
2. (Original post by KyleH123)
The principle quantum number:

Lowest energy electron of Krypton, it's quantum number would be 1, surely?
Highest energy of lithium would be 2?

Gah I hate doubting myself like this.
Yes
Yes
Hero
4. (Original post by KyleH123)
Hero
Principle quantum number is essentially a term for the number of energy levels/shells in an atom. Krypton has a quantum number 4 (as it has 4 energy levels) while lithium has a quantum number of 2.
Principle quantum number is essentially a term for the number of energy levels/shells in an atom. Krypton has a quantum number 4 (as it has 4 energy levels) while lithium has a quantum number of 2.
Yeah. Thanks a lot! :-)
Principle quantum number is essentially a term for the number of energy levels/shells in an atom. Krypton has a quantum number 4 (as it has 4 energy levels) while lithium has a quantum number of 2.
Not quite ..

The principle quantum number is the number of the energy level under discussion.

Krypton has four shells, each with a different principle quantum number.

You consider the position of an electron. It can be described by four quantum numbers, n, m, l & s

n = the energy level
m = the sub-shell
l = the azimuthal (magnetic orientation of the orbital)
s = the spin
7. (Original post by charco)
Not quite ..

The principle quantum number is the number of the energy level under discussion.

Krypton has four shells, each with a different principle quantum number.

You consider the position of an electron. It can be described by four quantum numbers, n, m, l & s

n = the energy level
m = the sub-shell
l = the azimuthal (magnetic orientation of the orbital)
s = the spin
God damn Charco, this is AS for crying out loud
God damn Charco, this is AS for crying out loud
9. (Original post by charco)
God damn Charco, this is AS for crying out loud
Hey guys. I was under the impression that the groups go like
Lithium Group 1 eg
Magnesium group 2, eg
and then everything inbetween group 2 and Boron is also group 2?

10. (Original post by KyleH123)
Hey guys. I was under the impression that the groups go like
Lithium Group 1 eg
Magnesium group 2, eg
and then everything inbetween group 2 and Boron is also group 2?

First two are correct, last line is wrong. Okay, we know that in group 1, there is Li and Na and that group 2 there is Mg and Ca. The "real" group 3 is the one containing scandium and yttrium, however, at A Level, we assume that the group that contains boron and aluminium is group 3(this group is called group 13 to account for the d block groups). So those elements in between group 2 and group 3 aren't group 2, but it doesn't matter for AS. You just have to be able to notice trends, write electron structures for them and know common ions, eg Fe2+, Fe2+, Cu2+ etc.

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Updated: October 11, 2016
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