Undergraduate - quantum numbers

If you draw the electron configuration in boxes like this:

Then one of each of the paired electrons is +1/2 and the unpaired ones are +1/2. So for N there are 5 electrons which are +1/2

Original post by charco

It is a bit vague as the spin quantum number is 's' and the magnetic quantum number symbol is 'm'.

There are four quantum number numbers (n,l,m,s) - you seem to be asked about the spin states of the electrons.

n = main energy shell or level (values 1,2,3 ..etc.)
l = type of sub-shell (values 0 ... n-1)
m = orbital within sub-shell (values -l,...0... +l)
s = spin state (plus/minus one half)

No two electrons can have all four quantum numbers the same.

Paired electrons have plus and minus one half. Single electrons have plus one half.

I believe that m is sometimes known as m(little l) and s is m(little s).... hence the ms the OP refers to is simply s

Original post by JMaydom

I believe that m is sometimes known as m(little l) and s is m(little s).... hence the ms the OP refers to is simply s

Reply 5

OP

Original post by Madasahatter

If you draw the electron configuration in boxes like this:

Then one of each of the paired electrons is +1/2 and the unpaired ones are +1/2. So for N there are 5 electrons which are +1/2

both paired AND unpaired +1/2??

Reply 6

OP

this is the ans but still dont get it

Every filled orbital has 1e with ms = +½ and 1e with ms = -½. Up to the 3p level, therefore, half of the electrons (9) have ms = +½. In the 4s orbital there is another electron with ms = +½. The d shell is not full, and again we cannot know whether the two electrons have ms = +½ or ms = -½. We do know that they will both be the same (Pauli principle). So there may be either 10 or 12 electrons with ms = +½.

Original post by The_Blade

this is the ans but still dont get it

Every filled orbital has 1e with ms = +½ and 1e with ms = -½. Up to the 3p level, therefore, half of the electrons (9) have ms = +½. In the 4s orbital there is another electron with ms = +½. The d shell is not full, and again we cannot know whether the two electrons have ms = +½ or ms = -½. We do know that they will both be the same (Pauli principle). So there may be either 10 or 12 electrons with ms = +½.

In every orbital the electrons are paired.

The electrons in the pair are assigned spin states of +½ or -½

Hence in a paired orbital there is one of each.

In degenerate orbitals the unpaired electrons have to have the same spin. Hence you dont know if they are +½ or -½.

It's actually bollox. The spin states are assigned artificially anyway.

Reply 8

Original post by The_Blade

both paired AND unpaired +1/2??

Yes. I have always considered the unpaired electrons to be assigned +1/2 the second electron in the orbital is assigned -1/2

Reply 9

OP

ok guys ive sat there on my chair and researched for about 1hr straight. and im stil unclear

1s2 2s2 2p6 3s2 3p6 3d2 4s2

how many e- that have ms=+1/2

if there are 22 e- in total surely half of then have ms=+1/2 and other half ms= -1/2

so why isnt the ans 11??

ans is 10 or 12...

Reply 10

Original post by The_Blade

ok guys ive sat there on my chair and researched for about 1hr straight. and im stil unclear

1s2 2s2 2p6 3s2 3p6 3d2 4s2

how many e- that have ms=+1/2

if there are 22 e- in total surely half of then have ms=+1/2 and other half ms= -1/2

so why isnt the ans 11??

ans is 10 or 12...

Half the paired electrons are +1/2. These are 1 in 1s, 1 in 2s, 3 in 2p, 1 in 3s, 3 in 3p, 1 in 4s. The 2 electrons in 3d are unpaired.

I always considered unpaired electrons as +1/2.

I make that 12.

Reply 11

OP

Original post by Madasahatter

Half the paired electrons are +1/2. These are 1 in 1s, 1 in 2s, 3 in 2p, 1 in 3s, 3 in 3p, 1 in 4s. The 2 electrons in 3d are unpaired.

I always considered unpaired electrons as +1/2.

I make that 12.

how do you know the 2 e in 3d are unpaired?

Reply 12

Hund's rule

It's like seats on the bus. Everyone takes a single seat until there are no more and then they are forced to pair up.

(edited 9 years ago)

Reply 13

OP