Electronic Structure

How many orbitals, electrons and pairs in an s sub-shell

1 orbital

2 electrons

1 pair

How many orbitals, electrons and pairs in p sub-shell

3 orbitals

6 electrons

3 pairs

How many orbitals, electrons and pairs in d sub-shell

5 orbitals

10 electrons

5 pairs

How many orbitals, electrons and pairs in an f sub-shell

7 orbitals

14 electrons

7 pairs

How many electrons can each main shell hold.

1st shell = 2

2nd shell = 8

3rd shell = 18

4th shell = 32

Energy levels of shells.

The further away from the nucleus the higher their energy level. (expect for 4s which is lower than 3d)

Because outer electrons are further away from the nucleus, so less electrostatic attraction between the outer electrons and nucleus with positive protons.

Electron occupation behaviour

• Always fill in the lowest energy sub-shell available

• They fill in each orbital that holds 2 electrons 1 after the other, never 2 at the same time because it’s more stable to do so, because otherwise the electrons would repel each other. (Bus seat rule)

Atoms in electron configuration

Fill in lowest energy sub-shells (move 1 electron from 4s to 3d sub-shell if the 3d sub shell is almost half full or almost full, so the electrons are more stable e.g chromium and copper atoms)

Rule for removing electrons to form transition metal ions

• Always remove electrons from the 4s sub-shell first until it is completely empty.

• If more electrons need to be removed, take them from the 3d sub-shell next