2014 DAT Destroyer Chem #311

[nickh]

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Hi guys,

For that question, it says the maximum number of electrons which can have a quantum number of N = 4 is 32, for N = 4, isn't the max 36? As seen in Kr? Or are they talking about something else here?

Thanks again!

 

[matardug]

In destroyer it is talking about energy level. So we use the 2n^2 rule. Plug in 4 for an energy level and we get 2(4)^2 = 32 in the fourth energy level. Meaning there is 4s^2 (2 electrons) 4p^6 (6 electrons) 4d^10 (10 electrons) and 4f^14 (14 electrons) adding we get 2+6+10+14 = 32

 

[nickh]

Hm... I wikied it, but didn't get much out of that article 😛 How important is this concept? Or do you think just by knowing the formula is enough? 🙂

 

[TheEpicFruitCake]

so here we have your quantum #'s

n = principal
l = azimuthal, can be anything (n-1)
m1 = magnetic (± l and 0, so azimuthal # X 2 + 1)
ms = spin (2 for each m up/down and represents the electron)

hopefully this rings a bell
n = 4
so l can = 3,2,1,0
for l= 3; m1 can be -3,-2,-1,0,1,2,3 (7 total); for each m1 there are 2 spins........ in total 14
for l = 2; m1 can be -2,-1,0,1,2 (5 total); for each m1 there are 2 spins ...... in total 10
for l = 1; m1 can be -1,0,1, (3 total); for each m1 there are 2 spins ...... in total 6
for l = 0; m1 can be 0 (1 total); for each m1 there are 2 spins ...... in total 2

14+10+6+2 = 32

 

[DAT Destroyer]

For the n=4 principle energy level of max of 32 electrons can be found, Kr is not a good example to illustrate this since all the electrons do not fill the 4th energy level and therefor not utilized

Hi guys,

For that question, it says the maximum number of electrons which can have a quantum number of N = 4 is 32, for N = 4, isn't the max 36? As seen in Kr? Or are they talking about something else here?

Thanks again!

For the n=4 principle energy level a max of 32 electrons can be found, Kr is not a good example to illustrate this since all the electrons do not fill the 4th energy level and therefor not utilized and are empty. A quick way to find max number of electrons for a given energy level is given by the 2n squared rule,

Hope this helps.

 

[DAT Destroyer]

Hm... I wikied it, but didn't get much out of that article 😛 How important is this concept? Or do you think just by knowing the formula is enough? 🙂

It is very important to know electron configuration and to know that the 4s energy level comes before 3d.

 

[FeralisExtremum]

nickh, I believe you're mixing up two separate concepts here.

Kr in an unexcited state has 36 electrons, cumulative, in all of its shells - in this case it has electrons in the 1st shell (2), 2nd shell (8), 3rd shell (18), and 4th shell (32 possible electrons in a 4th shell, but it only has 8). Hence Kr has 2 + 8 + 18 + 8 = 36 electrons total through its completely filled 1st, 2nd, 3rd, and partially filled 4th shells.

This is completely different than the question being asked, "the maximum number of electrons which can have a quantum number of N = 4", which essentially means "how many electrons are possible in the 4th shell". Not how many electrons are possibly cumulative throughout the first four shells, but how many are in just the 4th shell itself. In this case you would use the formula 2n^2, where n = shell #

This formula answers the question, but if I were you I would spend more time on studying electron orbitals, shells, electron configurations, quantum numbers etc. to gain a firm grasp on the subject. It's a fairly fundamental part of chemistry and making the mistake you did (while completely understandable) indicates you haven't quite learned it well enough just yet.

 

[nickh]

Oh... Okay, yeah I got it. So at N=4, it would contain S, P, D and F subshells, and each would have 2, 6, 10, 14 electrons respectively, in a total of 32 electrons.

Yeah for N=4, I was thinking the sum of electrons after the 4th period, while it was the quantum #, which contains the F subshell that was being asked in the question.

Yeah, I know electron configurations, but I wasn't clear on the nomenclature.

So it goes shell, which is the 1 2 3 4
Then sub shells, which are subshells that 1 2 3 4 has, =s for 1, s+p for 2, s+p+d for 3, and s+p+d+f for 4, but they are also called orbitals right? so subshells = orbitals?
Then there's specific orbitals, 1 for s, 3 for p, 5 for d, and 7 for f, and specific orbitals can have 2 electrons each
Then the arrows up and down for describing the electrons in specific orbitals are called spin

Yeah period refers to the periodic table, but N is referring to SPDF. Thanks guys for clearing it up 🙂