Atomic Structure and Introduction to Quantum Chemistry

Question 1

What is the range of IR?

Answer 1

1mm to 750nm

Question 2

What is the range of visible light?

Answer 2

750nm to 400nm

Question 3

What is the range of X-rays?

Answer 3

10nm to 1pm

Question 4

What is the range of UV?

Answer 4

400nm to 10nm

Question 5

What is the n=1 series of hydrogen spectra called?

Answer 5

The Lyman series

Question 6

What is the n=2 series of hydrogen specta called?

Answer 6

The Balmer series

Question 7

What is the n=3 series of hydrogen specta called?

Answer 7

The Paschen series

Question 8

What is the source of light in H emission spectra?

Answer 8

A voltage passed through a tube filled with H₂ gas

Question 9

What 2 objects do the light rays produced in a H emission spectra pass through before they are detected and what are their functions?

Answer 9

A slit to produce a single ray of light and a prism to seperate the light into its constituent wavelengths

Question 10

What are the rays of light produced for a H emission spectra detected by?

Answer 10

A photographic plate

Question 11

What is the Rydberg equation?

Answer 11

Where 1/λ and n₁<n>2</n>

Question 12

What can be intereprated about energy levels from the H emission spectra?

Answer 12

They have set energies at discrete energy levels. This is known as quantisation.

Question 13

What region of the EM spectrum do the Lyman series occupy?

Answer 13

UV

Question 14

What region of the EM spectrum do the Balmer series occupy?

Answer 14

Vis/UV

Question 15

What region of the EM spectrum do the Paschen series occupy?

Answer 15

IR

Question 16

What is significant about the relationship between Bohr’s equation and the Rydberg equations results.

Answer 16

As Rydbergs equation was derived from experimental data which results agreed with Bohrs results which was derived from theory, it proved Bohrs theory to be true.

Question 17

How do the Bohr model of the atom and the modern, quantum model of the atom differ?

Answer 17

The Bohr atom views electrons as particles whereas the quantum atom views electrons a spread out(delocalised) waves

Question 18

What 2 factors meant Bohr and his peers knew the Bohr model for an atom was wrong?

Answer 18

Particles moving a circle generate light which the electrons did not and what were stopping the electrons collapsing into the nucleus

Question 19

What kind of wave do electrons in orbit act like and what must be the case for this to occur?

Answer 19

A standing wave, for this the circumference of the orbit must be a multiple of the wavelength of the electron

Question 20

How can we prove that fitting more electrons into an orbit increases the energy of the orbit?

Answer 20

As more electrons fit into the orbit, the wavelength of each electrons standing wave must decrease meaning the energy increases as E∝1/λ

Question 21

What is the Schrödinger wave equation?

Answer 21

Where ψ is the wavefunction, H is the Hamitonian operator (contains terms to calculate energy), E is the total energy of the system

Question 22

What is the wavefunction, ψ?

Answer 22

It contains infromation about the behaviour of the system (e.g the position distribution of electrons) but has no simple physical meaning, it is just a mathematical function.

It can be understood as the equation of the ‘electron wave’ which could be something as simple as a sine wave or something very complex

Question 23

What is the Born interpretation of the wavefunction?

Answer 23

ψ² is the probability of finding an electron at a point in space

Question 24

For the ψ plots of the ‘particle in a box’, what do the waves look like for the 1st and 2nd solution, what does this mean for the ψ² values?

Answer 24

1st solution is 1/2 a wave, 2nd solution is a complete wave. The first solution has the highest probability of finding an electron in the centre of the box, the second solution has a node in the centre.

Question 25

What is the de Broglie equation?

Answer 25

λ=h/p=h/mv

Question 26

What is Heisenberg’s uncertainty principle and what is its meaning?

Answer 26

ΔpΔx≥h/4π

Where Δp is the uncertainty in momentum and Δx is the uncertainly in position.

This means the more we know about the postion of the electron, the less we know about its momentum and vice versa.

Question 27

What is the solution for the Schrodinger equation for a H atom and what does it give?

Answer 27

E_n=-hR/n²

Where n is the ‘principle quantum number’ and determines the energy of a given orbital

Question 28

What is the energy difference between the 2s and 2p energy levels for a hydrogen atom?

Answer 28

No difference, they are degenerate

Question 29

What does the wavefunction and wavefunction squared of an electron tell us about its atomic orbital?

Answer 29

The wavefunction tells us the about the x, y and z coordinates of the electron. The wavefunction² tells us about the probability of finding the electron.

Question 30

What proportion of the dots in a dot density of the plot are contained in a boundary surface line?

Answer 30

95%

Question 31

How are the lobes of the 2p_z orbital oriented?

Answer 31

Along the z axis

Question 32

What do different shading or +/- notation indicated about the atomic orbitals?

Answer 32

One has a positive amplitude of wavefunction, the other has a negative amplitude of wavefunction

Question 33

What are the orbitals of the d subshell called?

Answer 33

xy, yz, xz, x²-y², z²

Question 34

What do the xy, yz and xz orbitals of the d subshell look like?

Answer 34

4 lobes between the axis of the letters in the name

Question 35

What does the x²-y² orbital of the d subshell look like?

Answer 35

4 lobes along the x and y axis

Question 36

What does the z² orbital of the d subshell look like?

Answer 36

2 lobes along the z axis with a ring in the xy plane

Question 37

What are the 4 quantum numbers letters?

Answer 37

n, l, m_l and m_s

Question 38

What is the quantum number with the symbol n and what are its values?

Answer 38

The principal quantum number, it takes any integer value from 1 to infinity

Question 39

What is the quantum number with the symbol l and what values does it take?

Answer 39

The angular momentum quantum number and takes the integer values from 0 to n-1, e.g. for n=4, l=0, 1, 2, 3

Question 40

What is the quantum number with the symbol m_l and how many values does it have?

Answer 40

The magnetic quantum number and it has 2l+1 values, e.g. for l=2, m_l= -2, -1, 0, 1, 2

Question 41

What is the quantum number with the symbol m_s and what values does it take?

Answer 41

The spin quantum number and it can take the value of 1/2 or -1/2

Question 42

What letters do l=0, 1, 2 and 3 refer to?

Answer 42

0=s, 1=p, 2=d, 3=f

Question 43

What letter does the m_s=0 refer to? What about the other values of m_s?

Answer 43

The z orbitals, e.g. for l=1 m_s=0 is z, for l=2 m_s=0 is z². For the other values the more complex letters have higher values generally

Question 44

What is an atomic orbital?

Answer 44

A region of space that is occupied by an electron in an atom

Question 45

How do we adapt the Schrodinger equation for atoms with more than one electron?

Answer 45

We use orbital aproximation by combining wave functions for each electron.

Ψ(1, 2, 3…., N) = ψ(1) x ψ(2) x ψ(3) x……. ψ(N)

Question 46

How do orbitals in many electron atoms compare to electrons in a hydrogen atom?

Answer 46

Similar but many electron atoms change the effective charge on the electrons

Question 47

What is the order of electron shells filling up according to the Aufbau (building up) principle?

Answer 47

1s<2s<2p<3s<3p<4s<3d<4d<5s<4d<5p<6s

Question 48

What is the Pauli ‘exclusion’ principle?

Answer 48

Each orbital can contain a maximum of 2 electrons with opposite spins

Question 49

What letters denote different spins of electrons?

Answer 49

α for a spin of 1/2, β for a spin of -1/2

Question 50

In the mathematical form of the wavefunction, ψ = K.R(r).A(θ, φ), what are the names and function of each term?

Answer 50

K=normalising factor, a constant for a perticular system

R(r)=the radial wavefunction, it describes how wavefunction varies with distance from the nucleus

A(θ, φ)=the spherical harmonic, it describes how the wavefunction varies with angle around the nucleus (shape)

Question 51

For a plot of the radial parts of the atomic orbital wavefunctions, where do the graphs begin for each of the wavefunctions?

Answer 51

s orbitals=an arbitary y-intercept

all the other orbitals=the origin

Question 52

For a plot of the radial parts of the atomic orbital wavefunctions, what is the rule for how many radial nodes there is?

Answer 52

n-l-1 e.g. 1s=1-0-1=0 nodes, 3p=3-1-1=1 node

Question 53

What is the equation and definition of the radial distribution function(RDF)?

Answer 53

4πr²R(r)², it is the probability that an electron will be found at a given distance from the nucleus, regardless of the direction from it

Question 54

For a plot of the RDF, what is the rule for the number of peaks?

Answer 54

n-l

Question 55

For a plot of the RDF, what is the trend for the size of peaks?

Answer 55

The outermost peak is the largest, will inner peaks increasing in size up to it

Question 56

For a plot of the RDF, what are the y values at r=0 and ∞?

Answer 56

at r=0, RDF=0, as r=>∞, RDF=>0

Question 57

Why does the 3rd electron in Li experience much less nuclear charge than the 1st two electrons?

Answer 57

Because the 1st two electrons shield the 3rd electron by blocking the view of the electron to the nucleus

Question 58

What is penetration?

Answer 58

When an electron moves close to the nucleus, experiencing stronger attraction to the nucleus, but more repulsion by other electrons

Question 59

Why, in many electron atoms, is the 2s orbit lower in energy than the 2p orbit?

Answer 59

The 2s orbit penetrate closer to the nucleus than the 2p orbit and the 2p orbit is slightly shielded by the 2s orbit.

Question 60

What is Hund’s rule?

Answer 60

If a set of orbitals has the same energy, it is energetically favourable for electrons to enter different orbitals with the same spin

Question 61

What is the difference between a radial and angular nodes?

Answer 61

Radial nodes are spherical, angular nodes can be conical or planar