Unit 1A1 Atomic structure

Question 1

what is sub-atomic particle

Answer 1

proton, neutron, electron

Question 2

what is lower and higher energy level

Answer 2

lowest energy level is the one closest to nucleus

Question 3

what is relative mass of electron

diff to Alevel ocr A

Answer 3

1/1840

Question 4

mass in kg of electron

Answer 4

9.109 × 10‐³¹

Question 5

Mass number is?

Answer 5

number of proton + neutron represented by A

Question 6

Atomic number is?

Answer 6

Number of proton represented by Z

Question 7

Definition of isotopes?

Answer 7

atoms with same number of protons but different number of neutrons

Question 8

Properties of isotopes and why?

Answer 8

Same chemical properties but different physical properties

Because same electrons structure

Because physical properties rely on mass

Question 9

E.g. of physical properties?

Answer 9

Boiling point

Melting point

Density

Question 10

Name 5 stages of TOF

Answer 10

Ionisation

Acceleration

Ion Drift

Ion Detection

Data Analysis

Question 11

What is 2 type of ionisation?

Answer 11

Electron impact

Electrospray ionisation

Question 12

Describe electron impact?

Answer 12

High energy electrons fired to sample

electron gets knocked off

Atom gets ionised so cataion as lose electron

Question 13

Describe electrospray ionisation?

Answer 13

High voltage is applied to the sample(dissolved in a solvent)

Each particle is ionised by gaining a proton

Question 14

Describe acceleration?

Answer 14

Cation are accelerated by electric field to a constant kinetic energy

Rate of acceleration is dependent on mass

If lower mass it travels faster, if higher mass it travels slower velocity

Question 15

Describe ion drift?

Answer 15

• Ions are allowed to drift in a field-free region
• The time takes for the ions to reach a detector is measured
• ions with a low mass will reach the detector first, and those with a high mass
  will arrive last
• The mass of the ion can be determined from the time taken

Question 16

Describe ion detection?

Answer 16

• Positive ions that reach the detector pick up electrons and cause a current to flow in an
  ion-current detector
• The greater the abundance of the ion, the bigger the current produced
• The detector is linked to an amplifier and then to a recorder, which converts the current
  into a peak and that is shown in a mass spectrum
• The height of the peak is proportional to the size of the current generated, and
  therefore proportional to the abundance of the ion

Question 17

Describe data analysis?

Answer 17

• Flight times are analysed and recorded as a plot of abundance v mass/charge
  (m/z)
• Vertical scale sometimes carries no units

-The tallest peak is called the
base peak and sometimes is given the value of 100% for comparison purposes.

-The
higher the peak, the more abundant is the cation.

-So, the y-axis is also sometimes called
relative abundance. Sometimes the y axis is labelled abundance / %.

• The horizontal scale IS NOT JUST MASS but is m/z. What happens when z = 2?
• Molecules can be also ionised
• Or additionally, broken up into simpler particles by a process called fragmentation

Question 18

What is mass spectra?

Answer 18

graph which shows:
- the m/z for each ion on the x-axis
- the relative abundance for each ion on the y-axis

Question 19

Mass spectra can be used for?

Answer 19

• identify unknown elements
• calculate Ar values for known elements
• calculate the Mr values for molecular
  substances (elements or
  compounds)

Question 20

What is shell？

Answer 20

-Orbits of electron

-Each shell can contain a maximum number of electrons

• This number increases as the shells get further out since the volume available
  increases.
• Only 2 electrons can fit in the 1st shell but 8 can fit in the 2nd
• Moving out from the centre of the atom the shells are of higher energy.
• So, takes
  less energy to escape from the attraction
• These shells get closer to each other as they increase in energy
• Also shell can be referred as energy level

-Also each level has principal quantum number, n given

• As n increases the levels get closer until at n = infinity, the
  ‘edge’ of the atom is reached i.e. the electrons is now free from the nuclear attraction

Question 21

What is 4 types of sub-level and number of orbitals?

Answer 21

s - 1
p - 3
d - 5
f - 8

Question 22

What is nature of orbitals?

Answer 22

• e- are constantly moving so finding
  exact position is impossible
• However, regions where it is more
  probable to find an electron is known
• This region is called an orbital
• It different shape
• Some referred to as an electron cloud
• Each orbital holds 2 paired electrons and ‘spin’ in opposite directions

Question 23

What is shape of s and p orbitals?

Answer 23

s - spherical
p - dumb bell, can be x, y or z

Question 24

Rules for orbital filling?

Answer 24

• Electrons fill the lowest energy levels first.
• Each orbital has a maximum of 2 electrons.
• Two electrons in the same orbital have opposite spin.
• Orbitals of the same energy fill singly before pairing up

Question 25

Define first ionisation energy?

Answer 25

The energy required to remove one mole of
electrons from one mole of gaseous atoms

Question 26

3 factors deciding strength of ionisation energy?

Answer 26

• Larger nuclear charge leads to stronger attraction
• Larger radius/higher energy level leads to weaker attraction
• More shielding leads to weaker attraction

Question 27

What is general trend of ionisation energy in period?

Answer 27

• Ionisation Energy increases across a period
• The number of protons increase
• Shielding is constant / atomic radius decreases
• More energy is required to remove the electron

Question 28

What is exceptiona for trend of ionisation energy in period?

Answer 28

For group 3:
- Ionisation Energy decreases
- The electron is removed from a higher energy p sub-level
- Less energy is required to remove the electron

For group 6:
- Ionisation Energy decreases
- There is a pair of electrons in a p orbital
- Extra repulsion means less energy is required to remove the electron