electron structure

orbital

an orbital is a region around the nucleus which can hold up to 2 electrons with opposite spins

s orbitals

1 tells you that it is the lowest energy level (first shells)

the s tells you that the shape is spherical

each orbital can only hold 2 electrons

2nd energy level

can hold 8 electrons

in 4 seperate orbitals (2s, and 3 of 2p), each with two electrons

1×2s , 3×2p

filling p orbitals

fill each orbital singly before in pairs

this reduces repulsion

as electrons are negatively charged

3rd energy level

9 orbitals, can hold up to 18 electrons

1× 3s, 3×3p, 5×3d

order of filling up

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d

phrase about 4s

“4s fills first and empties first”

shortcut 1

shortcut 2

the p electrons can all be put together

you can put all the inner shell electrons together using the symbol for the previous noble gas and only expand on the outer electrons

Orbital exceptions

Copper, Chronium

4s should only be half filled as it is more stable that way

Cr: [Ar]3d⁵4s¹

Cu: [Ar]3d¹⁰4s¹

Nodes

nodes are the space between energy levels where electrons cannot exist

p orbitals have what shape

dumb-bell

Blocks of the periodic table

Groups 1 and 2: s-block because the highest occupied orbital is an s-orbital

Groups 3 to 0: p-block because the highest occupied orbital is a p-orbital

transition elements: d-block because the highest occupied orbital is a d-orbital

(3d is higher in energy than 4s)