electronic configuration

Question 1

formula for maximum no. of electrons in a shell:

Answer 1

2n^2

Question 2

shells are made of atomic orbitals - atomic orbitals definition:

Answer 2

a region around the nucleus that can hold up to two electrons, with opposite spins

Question 3

what is an s-orbital?

Answer 3

shape of a sphere - can hold up to 2 electrons

Question 4

what is a p-orbital?

Answer 4

dumb-bell shape, three separate p orbitals ( Px, Py and Pz) therefore in total, can hold up to 6 electrons as one orbital holds up to two electrons

Question 5

what are the d and f orbitals?

Answer 5

more complex shapes - but from the 3rd shell, five d-orbitals are present therefore 10 electrons in total as (each orbital can hold up to 2)
- from the 4th shell - seven f-orbitals present therefore 14 electrons in total

Question 6

how to fill each shell/what orbitals are in each shell and max no of electrons?
1st:
2nd:
3rd:
4th:

Answer 6

1st (n=1) shell - 1s (2 electrons)
2nd (n=2) shell - 2s, 2p (8 electrons)
3rd (n=3) shell - 3s, 3p, 3d (18 electrons)
4th (n=4) shell - 4s, 4p, 4d, 4f (32 electrons)

Question 7

why does the 4s subshell need to fill before the 3d subshell?
therefore order of filling?

Answer 7

because the 3d subshell is higher in energy, and orbitals fill in order of increasing energy
so order of filling is 3p, 4s, 3d

Question 8

in an electron in-a-box model, why must one electron occupy each box (orbital) before pairing starts?

Answer 8

to prevent any repulsion between paired electrons until there is no further orbital available at the same energy level

Question 9

how can you express electron configurations more simply eg
Na which is: 1s2 2s2 2p6 3s1

Answer 9

[Ne] 3s1

Question 10

why is the 4s sub shell emptied first during ionisation process?

Answer 10

since the energies of the 3d and 4s sub-shells are very close together, once both filled, the 3d energy level suddenly falls below the 4s energy level, therefore it’s emptied out first