L5/6 Electronic structure Flashcards
What is quantum theory?
= theoretical basis of modern physics that explains the nature and behaviours of matter and energy on the atomic and subatomic level
Explains:
- the spectra of light emitted by atoms
- that e- in atoms are stable & stay in their orbitals
- wave-particle duality = e- can behave as waves OR particles
What are energy levels?
= stable energy levels contain e- in the atom
- the absorption of energy (a photon of light) excites the e- causing them to jump to a higher energy level
- the e- jumping down emits a photon of light
*measuring the energy of the photon allows the energy difference between the energy levels to be calculated -> shows energy levels aren’t evenly spaced.
What is the 1st ionisation energy?
= the energy required to remove one mole of e- (to infinity) from one of gaseous atoms to form one of gaseous 1+ ions.
Does the 1st ionisation energy require energy?
Yes = endothermic because you are pulling apart between the e- and the positive nucleus.
What are the trend for ionisation energies in the periodic table?
- why?
- Decreases going down a group: going down a group the energy of the subshell (from which the e- is removed) and the shielding increases
- Increases going across a period: across a period atomic radius decreases so there is a greater attraction between e- and the positive nucleus.
What do successive ionisation energies prove?
The existence of quantum shells (s, p, d, f) because there is a large increase in ionisation from one shell to the next.
What is the 1st electron affinity?
= the energy required to add one mole of e- to one mole of gaseous atoms to produce one mole of gaseous 1- ions.
Do electron affinities require energy?
- 1st EA = exothermic/negative: gaining e- makes the system ore stable (great attraction between the positive nucleus + additional e-)
- The more exothermic the EA, the more stable the negative ion is formed
What are the trend for electron affinity in the periodic table?
- Becomes less negative (exothermic) going down a group
- Becomes more negative (exothermic) going across a period
What is an orbital?
= a region in space where there is a given (usually 95%) probability of finding a particular e-
-> the larger the quantum no. , the larger the orbital.
What shape is a:
- S orbital?
- P orbital?
- S = spherical
- P = ‘figure of eight’ shaped = two lobes with a nodal plane
What is a node?
= an area with no e-
What are shells?
= principle energy levels in poly-electron atoms, referred to by the letters: K, L, M, N
- They correspond to the principle quantum no. n
- n = a number greater than 0
- n = the no. of the period
- K n=1, L n=2, M n=3, N n=4
- Shells contain multiple orbitals (except n=1)
What are the principal quantum number?
- what does it indicate?
n = >0 = the period
Indicates:
- Distance of e- from the nucleus (the higher n the greater the distance)
- The e- energy (the high n the higher energy the e- has -> the further from the nucleus & easier to be removed)
- The no. of e- a shell can hold = 2n^2 e- maximum
e.g. L shell n=2 -> 2x2^2 = 8 e-
What are subshells?
= a group of orbitals with the same (equivalent) energy, referred to by the letters: s (sharp), p (principle), d (diffuse), f (fundamental)
- Described by the Azimuthal/subsidiary quantum no. l
- l = 0 -> (n-1)
What are the Azimuthal/subsidiary quantum numbers?
- what does it indicate?
l = 0 to (n-1)
Indicates:
- Which subshell an e- is in: l=0=s, l=1=p, l=2=d, l=3=f
- Energy of the subshell: energy increases as the vale of l increases
- Shape of the orbitals in that subshell: s=spherical, p=dumbell, d=more complex, f=even more complex
- The no. of e- a subshell can hold = 2(2l + 1)
e.g. l = 2 - d subshell that can hold 2(2x2 + 1) = 10 e-
What are the magnetic quantum numbers?
- what does it represent/indicate?
m = range = -l to 0 to +l
e.g. p: l=1, m= -1 to +1 -> 3 values=3p orbitals
Represents:
- The no. orbitals in the subshell
Indicates:
- The direction of a particular orbital to the magnetic field/axis
- The orientation of individual orbitals within a subshell
What are the spin quantum numbers?
- what do they describe?
s = -1/2 OR +1/2
Describes:
- The direction of the rotation of an e- around its own axis (self-rotation) as it moves around the nucleus.
- Clockwise spin (‘spin up’) = +1/2
- Anticlockwise spin (‘spin down’) = -1/2
- Orbitals have only 2 e- and they must have opposite spins (anti-parallel)
What are the equations for working out all the quantum numbers?
Principle: n = period = >0
Azimuthal: l = 0 to (n-1)
Magnetic: m = -l to 0 to +l
Spin: s = -1/2 OR +1/2
How many electrons can be in a shell?
2n^2
How many electrons can be in a subshell?
2(2l + 1)
What is Heisenberg’s Uncertainty principle?
= you cannot determine the position & momentum (velocity) of an e- at the same time.
What is the Aufbas principle?
= e- enter at the lowest available energy level first.
What is Hund’s rule of maximum multiplicity?
= when in orbitals of equal energy, e- will try to remain unpaired - minimises repulsion between like charges so they system is more stable.
What is the Pauli exclusion principle?
= no two e- can have the same four quantum numbers (n, l, m, s) and only two e- can share an orbital provided they have an anti-parallel spin.
What is the order for filling orbitals?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
What is Madeleines rule?
= Where you have two e- with equal n+l you fill the orbital with the lowest value of n first.
