LO's - inorganic chemistry Flashcards
Give the formula which links frequency, wavelength and the speed of light
c = fƛ
What are the units of wavelength?
nanometres (nm)
What is meant by the ‘dual nature of waves’ or ‘wave particle duality’?
Electromagnetic radiation can be described as both a wave (it has a wavelength and frequency) and a particle (stream of photons)
What are photons?
When electromagnetic radiation behaves more like a stream of particles, these particles are called photons
What happens to electrons when a photon is absorbed or emitted?
energy is lost or gained by electrons
What is the formula used to calculate the energy associated with a single photon?
E = hf or E = hc/ƛ
What is the formula used to calculate the energy associated with a mole of photons?
E = Lhf or E = Lhc/ƛ
What happens to electrons when energy is transferred to atoms?
electrons within atoms can be promoted to higher energy levels
What happens when an excited electron moves from a higher energy level to a lower energy level?
The atom emits a photon of light energy
What is an emission spectra and how can this be used to identify and quantify an element?
Produced when excited electrons move back down to a lower energy level. A spectrum made up of a series of lines at discrete (quantised) energy levels. Each line corresponds to the energy given out when an excited electron moves to a state of lower energy. No two elements produce the same emission spectra.
How does an emission spectra provide evidence for energy levels?
Each line corresponds to the energy given out when an excited electron moves to a state of lower energy.
What is an absorption spectrum and how is this produced?
The converse of an emission spectrum - where the continuous spectrum is seen, with black lines where radiation has been absorbed. Produced when electrons are promoted to a higher energy level by absorbing energy.
What is the link between intensity of radiation and concentration of the element present?
The intensity of radiation absorbed or emitted is proportional to the concentration of the element present.
What is an orbital?
Electrons can behave as waves - there are different shapes and sizes of waves around the nucleus, known as orbitals
How many electrons can an orbital hold?
2
Electrons within atoms have fixed amount of energy called…
quanta
What does the principal quantum number tell us?
indicates the main energy level for an electron and is related to the size of the orbital. ie. bigger n, bigger orbital
What does the angular momentum quantum number, l, tell us? What values can it have?
determines the shapes of the subshell. Has values from zero to (n-1). ie for n=3, l = 0,1,2
l = 0 s orbital l = 1 p orbital l = 2 d orbital l = 3 f orbital
What values can the magnetic quantum number, ml, have? What information does it give us about the electron?
determines the orientation of the orbital, has values from -l to +l
ie. l = 1 which is a p orbital has values of -1, 0 , + 1 (3 values because there are 3 orientations of a p orbital, px py pz)
What values can the spin quantum number, ms, have and what values can it have?
determines the direction of electron spin, can have values of +½ and - ½
Give the 1st and 2nd quantum numbers for the outer electron in a lithium atom
n = 2, l = 0
What is the ‘aufbau’ principle?
Electrons fill orbitals in order of increasing energy
What does Hund’s rule state?
When degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing starts
What does the Pauli exclusion principle state?
No two electrons in one atom can have the same set of 4 quantum numbers. Therefore, no orbital can hold more than two electrons and these two electrons must have opposite spins.
What does degenerate mean?
Having the same energy
(SKILL) Draw orbital box notation for the electron arrangement of an atom
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(SKILL) Write electronic configurations for each element up to atomic number 36
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Which is filled first: 3d or 4s?
4s
Ionisation energy increases across a period. Explain why there is a decrease from Be to B and from N to O
Special stability associated with a filled or half filled subshell (ie p subshell with 3 or 6 electrons). The more stable the electron arrangement is, the harder it is to remove an electron
(SKILL) Predict the shapes of molecules and polyatomic ions using VSEPR
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Name the arrangement of electron pairs around a central atom for: 2 electron pairs 3 electron pairs 4 electron pairs 5 electron pairs 6 electron pairs
linear trigonal planar tetrahedral trigonal bipyramidal octahedral
Explain how electron pairs repulsions affect the shape of a molecule
Electron pairs repulsions decrease in strength in the order:
non-bonding pair/non-bonding pair > non-bonding pair/bonding pair > bonding pair/bonding pair
