I dont understand atomic structure omg. pls help

davidche SG

1) Are the s, p, d, and f orbitals?

2) i tot in secondary school we learnt that first shell is 2 then second shell onwards are all 8 electrons. But using spdf, s has 2 electrons, then p has 6 and d has 10.

3) Whats the difference between the electrons in 3nd and 4rd level. Whats the difference between electrons in 3p and that in 4s level

4) still got more qns but cant think of them

dkcx SG

1) Yes they are

2) What you learn is still similar. Why you all learn it as 2,8,8,2 etc is becos the 3d shells are filled after the 4s and for O's you only study the 1st 20 without touching the 3d which begins at the 21st element and would be 2,8,9,2.

In the 1st shell, there is only 1 s orbital which contains 2 electrons so 1st shell max is 2.

2nd shell contains 2s 2p which is 2 + 6 = 8 electrons

3rd shell contains 3s 3p 3d which is 2 + 6 + 10 = 18 electrons

4th shell contains 4s 4s 4d 4f which is 2 + 6 + 10 + 14 = 32 electrons

3) Electrons in different shell have different energies. The higher the shell the more the energy. 3p is weaker than 4s.

Then general pattern is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d etc etc. Not very sure about the later 1s since i hardly use them.

However do note that some of the shells are very close in energy like 4s and 3d so there are times when the electrons filling don't follow that pattern eg in the case of Cr and Cu which is [Ar] 4s1 3d5 and [Ar] 4s1 3d10 instead of [Ar] 4s2 3d4 and [Ar] 4s2 3d9 cos the d shells is much more stable when partially/fully filled.

davidche SG

Thanks alot. Btw, whats the spdf notation of K(19 electrons) ? the place where i am stuck is after 1s2 2s2 2p6 3s2 3p6 do i move on to 3d1 or 4s1. If its 4s1, why so?

dkcx SG

4s1.

As i mentioned in the above, the order of filling the orbitals is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d etc etc

4s and 3d have very close energy levels so the only the 2 exceptions above for Cr and Cu have the 4s shells being incomplete. Thats the same for the elements below Cr n Cu which are the 5s 4d, 6s 5d but thats not important as all you will need know should be the special circumstances for Cr n Cu

speakup- SG

Adding to what dkcx mention, a more precise reason would be that a unfilled 4s orbital would be of lower energy level as compared to a 3d once hence contributing to its stability. Hence the electron preferentially occupies the 4s one first. For convenience go remember the order dkcx mentioned as it is damn helpful but its good to understand why the order is as such also.

iamapebble SG

Yupp you always fill in 4s before 3d. However when you write your ground state configuration, you label 3d first. Which means you put it as: 1s2, 2s2, 2p6, 3s2, 3p6, 3d8, 4s2 for example.

However, for energy level diagram, it should be:

_ _ _ _ _

_ _ _

So on and so forth.

As for removal of electrons(when they ask for configuration of ions for example), you always remove from the outermost shell first, which means you still remove from 4s first followed by 3d.