Chapter 2

Question 1

What is the use of a mass spectrometer?

Answer 1

It is used to determine the relative atomic masses (Ar) of elements and to determine the structure of organic compound

Question 2

What are the steps of a mass spectrometer?

Answer 2

1. the sample is first vaporised to form a gas
2. it is then bombarded by high energy elections to make positive ions (+1)
3. the positive ions are then accelerated in an electric field
4. the positive ions are then deflected in a magnetic field depending on their mass to charge ratio (m/z)
   - ions with a higher mass to charge ratio are deflected less in a magnetic field
5. finally, the positive ions reach the detector, where they produce a mass spectrum

Question 3

Bohr Model of an atom suggests….

Answer 3

electrons exist in energy levels or principal energy levels and can transition between these energy levels by absorbing or emitting exact amounts of energy. The principal energy levels are assigned numbers with n = 1 being closest to the nucleus and of lowest energy.

Question 4

The Pauli exclusion principle states…

Answer 4

two electrons cannot have the same quantum number. Simply put, two electrons can only occupy the same atomic orbital if they have opposite spins.

Question 5

Draw how orbitals spin

Answer 5

https://kognity-prod.imgix.net/media/edusys_2/content_uploads/2.2.4.1%20Two-electrons-in-the-same-orbital.a3ab008e7b8fdabfcabb.jpeg?w=1344&h=666&auto=compress

Question 6

Heisenberg’s uncertainty principle states…

Answer 6

it is not possible to know, at the same time, the exact position and momentum of an electron. Instead, we can only state the probability that an electron will be somewhere in a given region of space.

Question 7

Draw the graphs of orbitals s, px, py and pz

Answer 7

https://kognity-prod.imgix.net/media/edusys_2/content_uploads/s%20and%20p.5c710295e447111752e7.png?w=675&auto=compress

Question 8

Atomic Orbital

Answer 8

a region of space where there is a high probability of finding an electron

Question 9

The Afbau principle states…

Answer 9

electrons fill atomic orbitals of lowest energy first

Question 10

What order should sub-levels be filled?

Answer 10

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s

Question 11

Exceptions to the Afbau principle

Answer 11

Chromium:
- expected: 1s2 2s2 2p6 3s2 3p6 4s2 3d4
- reality: 1s2 2s2 2p6 3s2 3p6 4s1 3d5

Copper:
- expected: 1s2 2s2 2p6 3s2 3p6 4s2 3d9
- reality:1s2 2s2 2p6 3s2 3p6 4s1 3d10

Question 12

Line Spectra and elements

Answer 12

Different elements have different characteristic line spectra

Question 13

Electromagnetic Radiation

Answer 13

In order: radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), x-rays and gamma rays. These different types of EM radiation can be classified according to their energy, wavelength or frequency, going from longest wavelength to shortest

Question 14

Speed of light equation

Answer 14

3 x 10^8 = frequency (Hz) x wavelength (λ)

Question 15

Energy, frequency and wavelength

Answer 15

Higher energy = higher frequency = shorter wavelength.

Lower energy = lower frequency = longer wavelength.

Question 16

Infrared radiation

Answer 16

Infrared radiation has a longer wavelength, lower frequency and lower energy than visible light. Infrared radiation feels warm on the skin.

Question 17

Visible radiation

Answer 17

The visible region encompasses radiation of intermediate frequency. It is visible to the naked eye and takes on 7 different colours; red, orange, yellow, green, blue, indigo and violet.

Question 18

UV

Answer 18

The UV region encompasses UV radiation, which has a shorter wavelength and therefore a higher frequency and energy than visible light. This is the type of non-visible radiation emitted by the sun, which is dangerous for human skin.

Question 19

Dispersion

Answer 19

When white light passes through a prism, a continuous spectrum is produced. This separation of the white light into its component colours is known as dispersion.

Question 20

What does continuous spectrum show?

Answer 20

It shows all the wavelengths or frequencies of visible light

Question 21

What does an absorption line spectrum show?

Answer 21

It is similar to continuous spectrum, but it differs from a continuous spectrum in that some of the wavelengths of visible light are missing, shown by the black lines on the coloured background.

Question 22

What does an emission line spectrum show?

Answer 22

An emission line spectrum is characterised by having coloured lines on a black background

Question 23

How are emission line spectra made?

Answer 23

By absorbing or emitting energy, electrons can transition between the energy levels. If a high voltage is passed through a gas, the electrons in the gaseous atoms become excited and transition to higher energy levels. As the electrons fall back down to lower energy levels, the transitions are accompanied by an emission of energy. This results in the formation of an emission line spectrum.

Question 24

How are absorption line spectra made?

Answer 24

Absorption line spectra are produced when electrons absorb energy and transition to higher energy levels. Similar to the process of emission line spectra.

Question 25

Visible light and the use of energy while transitioning between energy levels

Answer 25

Electron transitions from n = 2 to higher energy levels absorb energy that corresponds to the wavelength or frequency of visible light. Electron transitions from n = 2 to n = 3, for example, absorb energy that corresponds to the wavelength of red light. Similarly, electron transitions from n = 2 to n = 5 absorb energy that corresponds to the wavelength of blue light.

Question 26

Draw a emission graph and an absorption graph

Answer 26

Emmision: https://kognity-prod.imgix.net/media/edusys_2/content_uploads/Nuclear%20fusion.b219db78a98f7654bd3c.png?w=825&auto=compress

Absorption: https://kognity-prod.imgix.net/media/edusys_2/content_uploads/24.3.1.6%20Electron%20transitions%20from%20n%202%20produce%20an%20absorption%20spectrum%20in%20the%20visible%20range.59943a304955f89826e5.png?w=825&auto=compress

Question 27

Energy equation

Answer 27

Energy (J) = h (Planck’s constant: 6.63 × 10-34 J s) x frequency (Hz)

Question 28

What can be deduced when looking the hydrogen emission line spectrum?

Answer 28

• Electron transitions to the n = 1 energy level emit energy that corresponds to the wavelength or frequency of ultraviolet (UV) radiation.
• Electron transitions to the n = 2 energy level emit energy that corresponds to the wavelength or frequency of visible light.
• Electron transitions to the n = 3 energy level emit energy that corresponds to the wavelength or frequency of infrared (IR) radiation.

Question 29

Lines in emission and absorption graphs

Answer 29

the longer the arrow, the greater the amount of energy emitted (or absorbed in the case of an absorption line spectrum)

Question 30

How line spectra give evidence for the model of an atom

Answer 30

We have seen that the line spectra are at characteristic frequencies for a given element. This shows that a given atom only emits certain energies, and the conclusion is that there are only certain energy levels available for the electrons in the atom. Electrons can transition from one energy level to another, but not to somewhere ‘in between’. Examination of line spectra gives evidence for the model of the atom in which electrons are arranged in different energy levels