Lecture 2 Flashcards
How do you find the energies of the subshells?
solve the Schrodinger equation
How do the energies of the orbitals differ within subshells in H atom?
In H atom orbitals within an n level all have the same energy
so 2p=2s
How do the energies of the orbitals differ within subshells in many electron atoms?
In many electron atoms, orbitals within a shell all have different energies
what are the 3 quantum numbers?
n, l, ml
What does n stand for?
principal quantum number
What does l stand for?
angular momentum quantum number
What does ml stand for?
magnetic quantum number
All orbitals with the same value of n belong to the same…
shell
e.g. 3
All orbitals of a shell that have the same value of l belong to the same…
subshell
e.g. 2p
Individual orbitals are identified by their value of…
ml
Describe principal quantum number
- n corresponds to the orbital energy level or
‘shell’. - Orbitals of a shell have the same energy and approximately the same radius.
- n is an integer with values from 1 to ∞.
Describe angular momentum quantum number
-Orbitals of each shell are divided into sub-shells, labelled by l.
-l determines the shape.
- For any principle quantum number n, l = 0, 1,…, n-1
Describe magnetic quantum number
- A subshell with quantum number l consists of 2l+1 individual orbitals.
- ml relates to the orientations of different orbitals.
- For a given value of l, ml takes the values l, l-1, l-2, 0,…-l.
How many subshells are there in the n=1 shell?
1
How many orbitals are there in a sub-shell that has l=2?
ml= -2, -1, 0, 1, 2
so 5 orbitals (d orbitals)
How are orbital names linked to quantum numbers?
- Orbitals are named after their quantum numbers
- First part of the name is the principal quantum number
- Second part of the name is linked to the orbital shape quantum number
- Subscripts after orbital names indicate the orbital orientation. These are the ml quantum number
values
e.g. l= 0 s orbital
l= 1 p orbital etc.
What is molecular bond theory?
- In the MO approach to bonding, wavefunctions are built up to describe the regions of space that the electrons occupy in the molecule.
- The electrons can be
delocalized across the entire molecule rather than localized in 2-centre bonds. - Molecular orbitals can be constructed from atomic orbitals for simple molecules.
Give the experimental facts of H2
- Element H exists as the H2 molecule.
- We can measure its bond length as 74 pm.
- It has a bond dissociation energy of 458 kJmol-1.
Give the chemistry of H2
- Colourless, odorless
- Highly combustible
Describe constructive interference
- arises when 2 waves are in the same phase when they combine
- results in a wave with greater amplitude than starting waves
(wavefunction has greater amp and wavefunction^2 also has greater amp so probability and electron density increases)
Describe destructive interference
- arises when 2 waves with different phases combine
- results in a wave with lower amplitude
