Week 1 Module 1

Question 1

What does the Lewis Dot Structure theory say?

Answer 1

That electrons like to be in pairs.

Question 2

What is the octet rule?

Answer 2

A molecule is more sable if the atom has 8 electrons in its outer shells.

Question 3

What is the issue of electrons being tiny magnets that attract each other?

Answer 3

Two negative charges repel each other.

Question 4

What is the structure of water and why? Thus, is water polar or non polar?

Answer 4

The structure of a water molecule is tetrahedral due to the repelling between electrons. Because of the uneven distribution in electrons, Water is a polar molecule.

Question 5

What are electrons like in O2?

Answer 5

6 valence electrons per oxygen, leaving to 12 in O2. 4 electrons are double bonded and the rest are lone pairs.

Question 6

Look at the Lewis Dot Structure and explain if O2 looks polar or non polar and thus if it is paramagnetic or diamagnetic.

Answer 6

The Lewis Dot Structure for Oxygen appears to be symmetrical which implies O2 is non polar. As electrons behave like tiny magnets, if it is symmetrical and non-polar, it should not interact with a magnet, yet, it does.

Question 7

What is the name of the new bonding model being taught?

Answer 7

Molecular Orbital Theory.

Question 8

What do you need to consider electrons as for the Molecular Orbital Theory to work?

Answer 8

As both particcles and waves.

Question 9

In an atom, what is the heaviest: the nucleus or the electrons?

Answer 9

The nucleus is way heavier than the electrons. A proton is ~1700 times heavier than an electron.

Question 10

Why don’t we fall through a chair when we sit on it?

Answer 10

Because electrons interact with pther electrons.

Question 11

Are electrons fast?

Answer 11

Electrons are able to move very quickly compared to the nucleus, and are thus too fast to be pinpointed, leading to some wave properties.

Question 12

Besides from electrons, what else has both wave and particle properties?

Answer 12

Light. Light has photons (particle) and electromagnetic radiation (wave-like).

Question 13

What are two wavelength examples?

Answer 13

Red and blue. Red is longer than blue and has lower energy.

Question 14

Explain sin diagram in terms of electrons.

Answer 14

Distance between two crests (maximums) is a wavelength (m/λ).
Cycles per second is frequency, ν (/s or Hz)

Question 15

How is λ and ν related?

Answer 15

ν (frequency) = c (speed of light) / λ (wavelength)

Question 16

What is the speed of light?

Answer 16

2.998 x 10^8 m/s

Question 17

What happens when light passes through 2 slits?

Answer 17

The waves interfere with each other, similar to ripples overlapping. - this is constructive and destructive interference.

Question 18

Explain that light has energy related to it’s wavelength.

Answer 18

This energy can efect electrons from a metal surface, only if this energy > threshold energy. (the metals work-function) - “photoelectric effect”.

Question 19

In what way can you think of orbitals?

Answer 19

As 3 dimensional electron waves.

Question 20

Show the way to work out Energy (?)

Answer 20

E = h (Plank’s constant) x ν = hc/λ (in J)
Can be rearranged to λ = hc/E
- Refer to bottom of page 3 for examples.

Question 21

What can you do if you know the frequency?

Answer 21

You can find the wavelength.

Question 22

If a wavelength is shorter, the energy is …?

Answer 22

Higher. Wavelength and frequencies are inversely proportional.

Question 23

What does s^-1 mean?

Answer 23

Hz.

Question 24

How do electrons act?

Answer 24

As charged particles with mass, m.

Question 25

How can electric fields affect electrons?

Answer 25

Electric fields can accelerate them to velocities, u.

Question 26

What is the equation for the kinetic energy of an electron?

Answer 26

E(kinetic) = (1/2) x m (mass) x u^2 (velocity) J

Question 27

What does the energy of an electron depend on?

Answer 27

Their velocities.

Question 28

What do electron wavelengths depend on, and thus what is the equation?

Answer 28

Their wavelengths depend on mass and velocity. λ = h / (m x u) m (?) - Example on middle of page 4.

Question 29

Do all electrons look the same? Are atoms just a dot? What are electron waves actually?

Answer 29

No. No. Orbitals.

Question 30

What is the main determining feature of Attractive Potential?

Answer 30

r - the distance from the point charge to the point being measured. (check later) Small r means a strong attractive potential.

Question 31

What prevents electrons from being attracted to the nucleus?

Answer 31

The wave properties. (refer to 2nd lecture ppt as we were cut off).

Question 32

Explain a mechanic of a wave

Answer 32

Bound at each end, oscillating with a particular frequency, - wave amplitude is 0 at extremes. n = 1 is the simplest wave. Orbitals are confined.

Question 33

How many nodes does the 1s and 2s orbitals have and what does it mean?

Answer 33

1s orbital has no nodes, 2s orbital has 2 nodes. More nodes mean a shorter wavelength.

Question 34

How should you visualise a 1D and 2D orbital

Answer 34

1D can be visualised as a guitar string, 2D as a drum head vibrating up and down.

Question 35

In a 2D wave, what is the part that does move called?

Answer 35

The node. (there are circular and linear nodes)

Question 36

How does a 2D wave work?

Answer 36

Oscillations above and below the plane. Diameter is λ/2 for fundamentral node.

Question 37

How are 2D waves represented?

Answer 37

Often as a contour plot or as loves of positive or negative displacement. Refer to page 5.

Question 38

Can 2D waves have waves where the left side vibrates in respect to the right?

Answer 38

Yes. Note. Circular wave is like an s-orbital. New one (?) is like a p-orbital.

Question 39

What can an overlap of d orbitals and p orbitals do?

Answer 39

Form a bond.

Question 40

Circle one that is cut into quatres has how many nodes? And what does it remind the teacher of?

Answer 40

2 linear nodes inbetween the changing phases, reminding him of a d-orbital.

Question 41

Orbitals (ψ) are also called?

Answer 41

A wave function. 1s orbital = 1s wave function.

Question 42

In 3D waves, what is the quantum description of electrons?

Answer 42

A standing wave.

Question 43

What is the definition for orbital?

Answer 43

The various wave functions, 𝜓, for the hydrogen atom. Often represented pictorially as a contour of constant |𝜓| such that the total charge outside the contour is small (e.g., 10%). Each orbital is specified by the three quantum numbers n, l and m l.

Question 44

How can a 1s orbital be represented and thought about as?

Answer 44

It can be represented by a perfect sphere, but thought of as a wave. Relevant to talk about radius.

Question 45

Refering to the graph drawn on page 6, what does the y axis represent and where is it most strong?

Answer 45

The y-axis represents the intensity/amplitude, with 𝜓 being the wave function orbital. The intensity is stronger closer to the origin.

Question 46

What can orbitals be used for?

Answer 46

To tell the energy of electrons. H𝜓 = E𝜓 H is kinetic potential.

Question 47

What is the knowing the probability of where an electron is vital for?

Answer 47

It is vital for a reaction.

Question 48

What do you get if you square the wave function?

Answer 48

The probability. 𝜓^2 = probability density. (positive and negative areas give the same 𝜓.)

Question 49

For 𝜓1s, the y-axis is the amplitude, while r is the distance from the origin. Squaring it suggests electrons are most likely at the nucleus. What is the problem with this and how do we fix this?

Answer 49

Being at the nucleus is impossible for the stability of the atom. To fix this, you multiple the square of the wave function x 4πr^2. This gives us the radial probability density.