LO's - inorganic chemistry

Question 1

Give the formula which links frequency, wavelength and the speed of light

Answer 1

c = fƛ

Question 2

What are the units of wavelength?

Answer 2

nanometres (nm)

Question 3

What is meant by the ‘dual nature of waves’ or ‘wave particle duality’?

Answer 3

Electromagnetic radiation can be described as both a wave (it has a wavelength and frequency) and a particle (stream of photons)

Question 4

What are photons?

Answer 4

When electromagnetic radiation behaves more like a stream of particles, these particles are called photons

Question 5

What happens to electrons when a photon is absorbed or emitted?

Answer 5

energy is lost or gained by electrons

Question 6

What is the formula used to calculate the energy associated with a single photon?

Answer 6

E = hf or E = hc/ƛ

Question 7

What is the formula used to calculate the energy associated with a mole of photons?

Answer 7

E = Lhf or E = Lhc/ƛ

Question 8

What happens to electrons when energy is transferred to atoms?

Answer 8

electrons within atoms can be promoted to higher energy levels

Question 9

What happens when an excited electron moves from a higher energy level to a lower energy level?

Answer 9

The atom emits a photon of light energy

Question 10

What is an emission spectra and how can this be used to identify and quantify an element?

Answer 10

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.

Question 11

How does an emission spectra provide evidence for energy levels?

Answer 11

Each line corresponds to the energy given out when an excited electron moves to a state of lower energy.

Question 12

What is an absorption spectrum and how is this produced?

Answer 12

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.

Question 13

What is the link between intensity of radiation and concentration of the element present?

Answer 13

The intensity of radiation absorbed or emitted is proportional to the concentration of the element present.

Question 14

What is an orbital?

Answer 14

Electrons can behave as waves - there are different shapes and sizes of waves around the nucleus, known as orbitals

Question 15

How many electrons can an orbital hold?

Answer 15

2

Question 16

Electrons within atoms have fixed amount of energy called…

Answer 16

quanta

Question 17

What does the principal quantum number tell us?

Answer 17

indicates the main energy level for an electron and is related to the size of the orbital. ie. bigger n, bigger orbital

Question 18

What does the angular momentum quantum number, l, tell us? What values can it have?

Answer 18

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

Question 19

What values can the magnetic quantum number, ml, have? What information does it give us about the electron?

Answer 19

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)

Question 20

What values can the spin quantum number, ms, have and what values can it have?

Answer 20

determines the direction of electron spin, can have values of +½ and - ½

Question 21

Give the 1st and 2nd quantum numbers for the outer electron in a lithium atom

Answer 21

n = 2, l = 0

Question 22

What is the ‘aufbau’ principle?

Answer 22

Electrons fill orbitals in order of increasing energy

Question 23

What does Hund’s rule state?

Answer 23

When degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing starts

Question 24

What does the Pauli exclusion principle state?

Answer 24

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.

Question 25

What does degenerate mean?

Answer 25

Having the same energy

Question 26

(SKILL) Draw orbital box notation for the electron arrangement of an atom

Answer 26

.

Question 27

(SKILL) Write electronic configurations for each element up to atomic number 36

Answer 27

.

Question 28

Which is filled first: 3d or 4s?

Answer 28

4s

Question 29

Ionisation energy increases across a period. Explain why there is a decrease from Be to B and from N to O

Answer 29

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

Question 30

(SKILL) Predict the shapes of molecules and polyatomic ions using VSEPR

Answer 30

.

Question 31

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

Answer 31

linear
trigonal planar
tetrahedral
trigonal bipyramidal
octahedral

Question 32

Explain how electron pairs repulsions affect the shape of a molecule

Answer 32

Electron pairs repulsions decrease in strength in the order:

non-bonding pair/non-bonding pair > non-bonding pair/bonding pair > bonding pair/bonding pair