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I find myself doubting myself. - Chemistry

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.

Reply 1

username2752874

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

Reply 2

KyleH123

Original post by GradeA*UnderA

Yes

Hero

Reply 3

username2752874

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.

Reply 4

KyleH123

Original post by GradeA*UnderA

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! :-)

Reply 5

charco

Study Forum Helper

Original post by GradeA*UnderA

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

Reply 6

username2752874

Original post by charco

God damn Charco, this is AS for crying out loud :wink:

Reply 7

charco

Study Forum Helper

Original post by GradeA*UnderA

God damn Charco, this is AS for crying out loud :wink:

Reply 8

KyleH123

Original post by charco

Original post by GradeA*UnderA

God damn Charco, this is AS for crying out loud :wink:

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?

I think I'm wrong about this.

Reply 9

username2752874

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?

I think I'm wrong about this.

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.