Structure 1.3

Question 1

Describe the hydrogen emission spectrum

Answer 1

It is a series of:
1. Individual-coloured lines
2. Of specific wavelengths
3. On a dark background
4. the converge at higher energy
5. and reflects the discrete energy levels present in a hydrogen atom.

Question 2

How does the hydrogen emission spectrum relate to hydrogen?

Answer 2

Each line in the hydrogen emission spectrum corresponds to the release of energy when an electron of hydrogen de-excites from from a higher energy level to a lower energy level

Question 3

Why do different metals produce different-coloured flames during flame tests?

Answer 3

Electrons of the metals are first promoted to a higher energy level by the heat of the flame.

Since the different metals have different energy levels, when these electrons de-excite to a lower energy level, photons of specific wavelengths are emitted, hence causing each metal to produce its own specific colour.

Question 4

How to calculate speed of light?

Answer 4

Speed of light = frequency (Hz) x wavelength (m)

Question 5

How calculate energy of a photon?

Answer 5

Energy = planck constant x frequency (m)
Energy = (planck constant x speed of light) / wavelength

Question 6

How does the line emission spectrum provide evidence for discrete energy levels?

Answer 6

1. Each coloured / dark line corresponds to one wavelength or frequency, and represents photons of a specific energy.
2. When the atom de-excites, photons are emitted with energy equal to the difference in energy levels of the atoms.
3. Since the energy of a photon is given by E = hf, this implies that there is a specific energy change of an orbital electron between energy levels in the atom.

Question 7

State aufbau’s principle

Answer 7

Orbitals of the lowest energy are filled first.

Question 8

State pauli’s principle

Answer 8

1. Each orbital holds a maximum of 2 electrons, 2. and these electrons must have opposite spin.

Question 9

State hund’s principle

Answer 9

Before pairing occurs:
1. Orbitals must have filled singly
2. with parallel spins
3. this ensures that electrons are as far apart as possible to minimise electronic repulsion.

Question 10

Why are copper and chromium exceptions?

Answer 10

Both elements only have 1 electron in the 4s subshell.

Question 11

State the electronic configuration of copper

Answer 11

1s2 2s2 2p6 3s2 3p6 3d5 4s1

Question 12

State the electronic configuration of chromium

Answer 12

1s2 2s2 2p6 3s2 3p6 3d10 4s1

Question 13

Why do copper and chromium only have 1 electron in the 4s subshell?

Answer 13

The electronic configurations in which all orbitals of the same subshell that are either half-filled or fully-filled will have a relatively mor symmetrical distribution of electrons and therefore greater stability.

Question 14

Definition of 1st I.E.

Answer 14

The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous cations.

Question 15

Calculate ionisation energy

Answer 15

energy x 6.02 x 10^23