Lecture 1 Flashcards
What is an atomic orbital?
region of space that is occupied by an electron in an atom
Describe electron density plots
Electron density or probability density representations of electrons in atoms describe the electron as located within a specific region of space (the atomic orbital) with a particular electron density at each point in space
What is the ground state?
the lowest energy state for an electron in H atom
What does dense dots in the plot mean?
area/place where theres a big chance of finding an electron
What is a boundary surface representation?
- A boundary surface picture is a simple single line plot that denotes the shape of the orbital.
- The boundary surface line is drawn so that it encloses -95% of the probability of finding an electron.
- These are often found in textbooks
Describe the boundary surfaces of s orbitals
- spherically symmetrical
- nucleus is at the centre
- no nodal planes in the surface boundary
Describe how the boundary surface changes as you go from 1s,2s and 3s
Orbitals get bigger and increase in energy
Why do orbitals increase in energy as they get bigger?
As electrons get more spread out/more delocalised, theyre interacting less with positive nucleus so more energy
What is a node?
empty white band called the nodal region has 0 probability of finding an electron
How many nodes does 2s orbital have?
1 node
How many nodes does 3s orbital have?
2 nodes
How do nodes influence energy of orbitals?
more nodes= high energy of orbital
Describe the boundary surfaces of p orbitals
- 3 p orbitals of a shell are identical
- px, py, pz labels are used instead of m quantum number labels
- nodal plane runs through the nucleus
- different coloured lobes= different amplitude of wavefunction
Describe the boundary surfaces of d orbitals
- 2 nodal planes runs that intersect at the nucleus, except for dz^2 (2 nodal cones)
- different coloured lobes= different amplitudes of wavefunction
What is the mathematical forms of wavefunction?
All orbitals have the form;
Ѱ = R(r) . A(θ, φ)
- R(r)= the radical wavefunction,
describes how wavefunction varies with distance from the nucleus (r=distance of electron from nucleus) - A(θ, φ)= the spherical harmonic,
describes how wavefunction varies with angle around the nucleus. (shape)
Describe and draw the graph of R(r) against r for 1s orbital
negative exponential graph
doesnt touch x axis as has no nodes
What is radical nodes?
- Points at which the radical wavefunctions pass through 0 are called ‘radical nodes’
- An s orbital has a non-zero amplitude at the nucleus. all other orbitals are zero at the nucleus
- All orbitals go to zero at large distances from the nucleus
Draw the graph of R(r) against r for 2s orbital
Draw the graph of R(r) against r for 2p orbital
How are phases between orbitals different?
- 2 different lobes can have different phases (+ and -)
How do you know whether wavefunction has a positive or negative phase?
- a positive amplitude shows a positive phase.
the wave will be above 0 on a graph - a negative amplitude shows a negative phase.
the wave will be below 0 on a graph
Describe the phase and nodal properties of a s orbital. Draw a phase diagram
- spherically symmetrical
- boundary surface has a single phase (always + or -)
Draw the phase diagram and graph for p orbital
