H2 Chem Atomic Structure Cheat Sheet

Representation	Proton number: no of proton	Nucleon number: no of proton and neutron
Isotopes	atoms of same element with different no of neutron	i.e. same no of proton, diff no of neutrons
	same no of e^- = same chemical properties	diff no of neutron = diff mass = diff physical properties

3 levels
Principle quantum shell	Energy band of shells separated by large energy gap	Numbered (1,2,3)	specifies energy of e^-, size of orbital, avg distance from nucleus
	Higher no =	further from nucleus = less strongly attracted	higher energy level of e^-
Subshell	group of orbitals which share same shape and properties	4 types: s, p, d, f	Energy: s<p<d<f
Orbitals	region of space with high possibility (>95%) of finding e^-	each orbital can hold max 2 e^-, and must be of opp spin
	s orbital	spherical
	p orbital	dumbbell along axis	px, py, pz
	d orbital	2 dumbbells on plain	d(xy), d(yz), d(xz)
		2 dumbbells cutting axis	d(x²-y²)
		dumbell cutting z-axis, donut at the centre	d(z²)
	f orbital	NOT IN SYLLABUS

Strength of electrostatic forces of attraction felt by valence e^- after accounting for shielding effect of inner electrons
	Z(eff) = Z - S
	Z: nuclear charge	size of positive charge (no of protons)	larger = stronger EFoA
	S: shielding effect	decrease in EFoA btwn nucleus and e^- due to repelling effect of inner e^-
		no of inner e^- (no of inner PQN/ subshell)	more = weaker EFoA btwn nucleus and e^-

energy required to remove 1mol of e^- from 1mol of gaseous atoms to form 1mol of singly charged gaseous cations (1st IE)
Breaking EFoA = endothermic = always +ve
Subsequent IE always greater than previous	stronger EFoA between more +vely charged nucleus and e	Z incr -> Z(eff) incr -> more E to overcome
Trend
Down group	Z incr, but S incr more significantly => Z(eff) decr	valence e^- to be removed are further from nucleus
	= EFoA decr	= less E req. to remove e^-
	= decr in IE
Across period	S almost same as same PQN	Z incr as proton no incr	= Z(eff) incr
	= incr EFoA	= more E req. to remove e^-
	= incr in IE
Anomaly: within period	G2 > G13	p-orbital e^- at higher E than s-orbital e^_
		= less E req to be ionised
	G15>G16	e^_ from G16 is paired	= inter-e^_ repulsion in same orbital
		= less E req to ionise completely
When answering	1. write both electronic config
	2. change in Z, S, PQN, Z(eff)
	3. change in EFoA and E req.
	4. Effect on IE
Successive IE of an element	singly -> doubly charged	doubly -> triply charged
	Z remains same (for same element), S decr => Z(eff) incr
	= more E req to overcome
		Large incr in IE => change in PQN

Arrangement of e^- in their principal quantum shells, subshells and orbitals
Rules for arrangement	Pauli's exclusion principle	each orbital holds max 2 e^-, in opp spin
		each e^- is a half arrow	opp spin = 1 point up, other point down
	Hund's rule	orbitals must be singly occupied first w/ parallel spin before pairing	to minimise inter-e^- repulsion
	Aufbau principle	e^- in ground state goes into empty orbital w/ lowest energy, before filling up next orbital of lowest energy
		as PQN incr, energy ga between sucessive shell decrease	eventually overlaps/converges
		3d vs 4s: fill and remove from 4s first	4s lower E when empty, higher E when filled
3 representation
Written	1s2 2s2 2p6 3s2 3p6 4s2 3d7
	write 3d before 4s as 4s is higher energy
	Anomaly for Cr and Cu	Expected: [Ar] 4s2 3d4 or 3d9	Actual: Expected: [Ar] 4s1 3d5 or 3d10
		symmetrical 3d cloud more energetically favourable	close E levels allow for rearrangement
Drawn config	Draw lines representing orbitals	fill up with e^- accordingly
Energy level diagram	y axis: E level	.
	each subshell occupies the same E level	.
	spaces btwn subshell decrease as E incr	.

H2 Chem Atomic Structure Cheat Sheet (DRAFT) by L_Wen