Structure and Bonding Flashcards
E =
n^2h^2 / 8(me)L^2
in 2D n^2 becomes n^2 + m^2
3 angular wave functions of p orbitals
px, (orbital horizontal, x horizontal axis, y vertical axis)
py, (orbotal vertical, x horizontal axis, y vertical axis)
pz, (orbital horizontal, z horizontal axis, x vertical axis)
Half equations: IO3 - goes to what in 4 - 9M HCl?
ICl2 -
Define quantize
To restrict a quantity to one of a fixed set of numbers
What is the experimental evidence for electrons behaving as both a particle and a wave
The photoelectric effect - many metals emit electrons when light shines on them. Increasing intensity of light increased number of electrons emitted, but not their kinetic energy - so electrons behave as particles
Davisson and Germer (1925) - Fired electrons at nickel. Electrons diffracted not just reflected - a property of waves
De Broglie relation
λ = h /mv
KE =
Curvature = 2nd derivative
Typical bond length in a molecule
100 pm
A very small wavelength means…
no diffraction
What is the potential energy of an electron confined to a 1D box?
0 inside the box, infinity at the walls
What is the wavefuntion, ψ?
Wave height at point x
When you put an electron in a box…
It behaves as a wave
ψn(x) =
Csin(nπx / L)
L = length of box n = quantum number C = normalisation constant, value needed to make integral of this 1
What is a node?
Locus where the wavefuntion is 0
What is ψ^2?
The probability of finding the electron at that point
ψ(n,m) (x,y)
2/L sin(nπx/L) sin(mπy/L)
Quantum number n =
Orbital size quantum number - principle quantum number
Quantum number l =
Orbital shape quantum number - orbital angular momentum quantum number
Quantum number ml =
Orbital orientation quantum number - magnetic quantum number
Orbital is another word for…
hydrogen wave function, ψ
What does it mean to say that the electron can behave as a wave as long as it’s a standing wave?
The wave must be continuous, and there must be an integer number of waves around the ring
2πr =
nλ
What is the radial wavefunction?
Depends on radius r, quantum number n = 1,2,3,4….
Uses symbol ψ(r)
What is the angular wavefunction?
Depends on θ, ϕ, quantum numbers l (0 , 1, …. , n-1) and ml (-l, …, +l)
Uses the symbol ψ(θ, ϕ)
What is needed to give a wavefunction in spherical polar coordinates?
Radius, r
Colatitude (angle down from z axis), θ
Azimth (angle east from x-z plane), ϕ
What quantum numbers give a 1s wavefunction?
n = 1
l = 0
ml = 0
(s means l = 0)
Radial distribution function =
4πr^2ψ^2
The probability of finding the electron in all directions at that radius
How many radial nodes does an ns wavefunction have?
n-1
np = n-2 nd = n-3
Total wavefunction =
ψ(r)ψ(θ,ϕ)
Angular wave functions for all s wave functions are…
spherical
What is the boundary surface?
A representation of the angular wavefunction that contains 90% of the electron density
If 2 energy states are degenerate they…
have the same energy
What is the Pauli Exclusion Principle?
No 2 electrons in an atom or ion can have all their quantum numbers the same
What is Hand’s rule of maximum spin multiplicity?
Lowest energy = maximum number of parallel spins
For hydrogen, orbital energy is proportional to…
-1/n^2
For atoms other than hydrogen, orbital energy is proportional to…
-Zeff^2 / n^2
Order of repulsion of electron pairs (strongest to weakest)
Lone pair - lone pair
lone pair - bonding pair
Bonding pair - bonding pair
Shape and bond angle of molecule with 2 electron pairs
Linear
180
Shape and bond angle of molecule with 3 electron pairs
Trigonal planar
120
Shape and bond angle of molecule with 4 electron pairs
Tetrahedral
109.5
Shape and bond angle of molecule with 5 electron pairs
Trigonal bipyramid
90 and 120
Equatorial larger site
Shape and bond angle of molecule with 6 electron pairs
Octahedral
90
Shape and bond angle of molecule with 7 electron pairs
Pentagonal bipyramid
90 and 72
Axial larger site
What is Bent’s rule? (VSEPR)
The smaller atom goes to the smaller site
Why do we need to create orbital hybrids?
Because for overlap we need singly occupied orbitals
What hybridisation does forming a linear molecule require?
sp
What hybridisation does forming a trigonal planar molecule require?
sp2
Taking s, px, py and 3 hybrids at 120degrees in the xy plane
What hybridisation does forming a tetrahedral molecule require?
sp3
Taking s, px, py and 4 hybrids directed at the vertices of the tetrahedron
The anti bonding orbital is denoted by…
σu* or πg*
The bonding orbital is denoted by…
σg or πu
Bond order =
(no of bonding electrons - no of anti bonding electrons) / 2
What does paramagnetic mean?
A material is paramagnetic if it is attracted to a magnet because of unpaired electrons
What does diamagnetic mean?
A material is diamagnetic if it is repelled by a magnet because of paired electrons
Molecular orbitals are…
linear combinations of atomic orbitals
Magnetic moment, X =
diamagnetic - paramagnetic
For diatomic molecules with p orbitals, σu* =
1/√2 [pz(a) + pz(b)]
For diatomic molecules with p orbitals, σg =
1/√2 [pz(a) - pz(b)]
For diatomic molecules with p orbitals, πu =
1/√2 [px(a) + px(b)]
For diatomic molecules with p orbitals, πg* =
1/√2 [px(a) - px(b)]
Bond order will correlate with…
Bond length and bod strength
J in SI base units
kg m^2 s^-2
What is excitation energy?
The energy required to move and atom to its next energy level
1 mile =
1609 m
What is more penetrating, 2p or 2s?
2s
If an orbital is more penetrating, it feels…
a higher Zeff
What is penetration?
The attraction an orbital feels towards the nucleus
How to show if an orbital has a higher Zeff than another
Sketch the radial distribution functions, whichever has a local maximum closest to the nucleus feels a higher Zeff
State and explain for which elements sp switching occurs
B, C and N
2p orbitals are not involved with elements before B. After N, the energyy gap between 2s and 2p is too large
σg and πu switch
Describe the 1s, 2s and 3s wavefunctions and radial wavefunctions
All start at not 0,
Have 0, 1 and 2 nodes respectively and tend towards x axis
Radial wavefunctions are bumps, starting at 0, going to 0 at nodes, tending towards x axis
Describe the 2p and 3p wavefunctions and radial wavefunctions
Start at 0, go up first
Have 0 and 1 nodes respectively
Tend towards x axis
Radial wavefunctions are bumps, starting at 0 going to 0 at nodes, tending towards x axis
Describe the 3d wavefunction and radial wavefunction
Starts at 0, goes up first, no nodes
Tends towards x axis
Radial wavefunction similar shape, goes up higher, more like a bell
