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.
