Week 1 Module 1 Flashcards
What does the Lewis Dot Structure theory say?
That electrons like to be in pairs.
What is the octet rule?
A molecule is more sable if the atom has 8 electrons in its outer shells.
What is the issue of electrons being tiny magnets that attract each other?
Two negative charges repel each other.
What is the structure of water and why? Thus, is water polar or non polar?
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.
What are electrons like in O2?
6 valence electrons per oxygen, leaving to 12 in O2. 4 electrons are double bonded and the rest are lone pairs.
Look at the Lewis Dot Structure and explain if O2 looks polar or non polar and thus if it is paramagnetic or diamagnetic.
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.
What is the name of the new bonding model being taught?
Molecular Orbital Theory.
What do you need to consider electrons as for the Molecular Orbital Theory to work?
As both particcles and waves.
In an atom, what is the heaviest: the nucleus or the electrons?
The nucleus is way heavier than the electrons. A proton is ~1700 times heavier than an electron.
Why don’t we fall through a chair when we sit on it?
Because electrons interact with pther electrons.
Are electrons fast?
Electrons are able to move very quickly compared to the nucleus, and are thus too fast to be pinpointed, leading to some wave properties.
Besides from electrons, what else has both wave and particle properties?
Light. Light has photons (particle) and electromagnetic radiation (wave-like).
What are two wavelength examples?
Red and blue. Red is longer than blue and has lower energy.
Explain sin diagram in terms of electrons.
Distance between two crests (maximums) is a wavelength (m/λ).
Cycles per second is frequency, ν (/s or Hz)
How is λ and ν related?
ν (frequency) = c (speed of light) / λ (wavelength)
What is the speed of light?
2.998 x 10^8 m/s
What happens when light passes through 2 slits?
The waves interfere with each other, similar to ripples overlapping. - this is constructive and destructive interference.
Explain that light has energy related to it’s wavelength.
This energy can efect electrons from a metal surface, only if this energy > threshold energy. (the metals work-function) - “photoelectric effect”.
In what way can you think of orbitals?
As 3 dimensional electron waves.
Show the way to work out Energy (?)
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.
What can you do if you know the frequency?
You can find the wavelength.
If a wavelength is shorter, the energy is …?
Higher. Wavelength and frequencies are inversely proportional.
What does s^-1 mean?
Hz.
How do electrons act?
As charged particles with mass, m.
How can electric fields affect electrons?
Electric fields can accelerate them to velocities, u.
What is the equation for the kinetic energy of an electron?
E(kinetic) = (1/2) x m (mass) x u^2 (velocity) J
What does the energy of an electron depend on?
Their velocities.
What do electron wavelengths depend on, and thus what is the equation?
Their wavelengths depend on mass and velocity.
λ = h / (m x u) m (?)
- Example on middle of page 4.
Do all electrons look the same?
Are atoms just a dot?
What are electron waves actually?
No.
No.
Orbitals.
What is the main determining feature of Attractive Potential?
r - the distance from the point charge to the point being measured. (check later)
Small r means a strong attractive potential.
What prevents electrons from being attracted to the nucleus?
The wave properties.
(refer to 2nd lecture ppt as we were cut off).
Explain a mechanic of a wave
Bound at each end, oscillating with a particular frequency,
- wave amplitude is 0 at extremes.
n = 1 is the simplest wave.
Orbitals are confined.
How many nodes does the 1s and 2s orbitals have and what does it mean?
1s orbital has no nodes, 2s orbital has 2 nodes.
More nodes mean a shorter wavelength.
How should you visualise a 1D and 2D orbital
1D can be visualised as a guitar string, 2D as a drum head vibrating up and down.
In a 2D wave, what is the part that does move called?
The node. (there are circular and linear nodes)
How does a 2D wave work?
Oscillations above and below the plane. Diameter is λ/2 for fundamentral node.
How are 2D waves represented?
Often as a contour plot or as loves of positive or negative displacement.
Refer to page 5.
Can 2D waves have waves where the left side vibrates in respect to the right?
Yes.
Note. Circular wave is like an s-orbital. New one (?) is like a p-orbital.
What can an overlap of d orbitals and p orbitals do?
Form a bond.
Circle one that is cut into quatres has how many nodes? And what does it remind the teacher of?
2 linear nodes inbetween the changing phases, reminding him of a d-orbital.
Orbitals (ψ) are also called?
A wave function.
1s orbital = 1s wave function.
In 3D waves, what is the quantum description of electrons?
A standing wave.
What is the definition for orbital?
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.
How can a 1s orbital be represented and thought about as?
It can be represented by a perfect sphere, but thought of as a wave.
Relevant to talk about radius.
Refering to the graph drawn on page 6, what does the y axis represent and where is it most strong?
The y-axis represents the intensity/amplitude, with 𝜓 being the wave function orbital. The intensity is stronger closer to the origin.
What can orbitals be used for?
To tell the energy of electrons. H𝜓 = E𝜓
H is kinetic potential.
What is the knowing the probability of where an electron is vital for?
It is vital for a reaction.
What do you get if you square the wave function?
The probability.
𝜓^2 = probability density.
(positive and negative areas give the same 𝜓.)
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?
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.
