Atomic Structure Flashcards

1
Q

Two lead isotopes were analysed in a TOF mass spectrometer.
Ions of both isotopes were accelerated with the same kinetic energy
207^Pb took 1.67 x 10^-5 s to travel through the mass spectrometer tube
Calculate the time taken for the 211^Pb ion to travel through the spectrometer

A

KE= 0.5 x m x v^2 so…
0.5 x (m of 207^Pb) x (d^2/t^2) = 0.5 x (m of 211^Pb) x (d^2/t^2)
can be simplified to…
(207 / 1.67 x 10^-5) = (211 / t^2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is electrospray ionisation carried out?

A

Dissolved sample injected through a hypodermic needle at a high voltage, it gains a H+ ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Give an equation for electrospray ionisation

A

X(g) + H+ –> XH+(g)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How is electron impact ionisation carried out?

A

Dissolved sample fired through high energy electrons, ‘knock off’ an electron from the atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Give an equation for electron impact ionisation

A

X(g) –> X+(g) + e-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What equation can be used to find the mass of one atom?

A

mass of one atom = Ar / L (6.022 x 10^23)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Explain why it is necessary to ionise molecules when measuring their mass in a TOF mass spectrometer

A
  • need to be ions in order to interact with and be accelerated by an electric field
  • Only ions will create a current when hitting the detector
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Chlorine exists as two isotopes 35Cl and 37Cl in the ratio 3:1
Give a statement describing the peaks that would appear in the mass spectrum of Cl2

A

Peaks at m/z = 70, 72 and 74 in the ratio 9:6:1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the definition of relative atomic mass?

A

the average mass of all atoms in an element relative to 1/12 mass of a C atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why do isotopes have similar chemical properties?

A

they all have the same electronic structure (configuration)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

State and explain the trend in the first ionisation energies of the elements in Group 2 from magnesium to barium

A
  • Decrease
  • Ions get bigger / more (energy) shells
  • Weaker attraction of ion to lost electron
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

State and explain which of the elements magnesium and aluminium has the lower first ionisation energy

A
  • Al
  • (Outer) electron in (3)p orbital
  • Higher in energy / further from the nucleus so easier to remove
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the plum-pudding model?

A

the model of the atom suggesting that atoms were small spheres of positive matter, with negative charge/electrons distributed throughout

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the relative mass of an electron?

A

1/1840

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is an isotope?

A

atoms of the same element with the same atomic number of P+ and e-, but a different number of neutrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How are ions accelerated in TOF mass spectroscopy?

A

accelerated to the same KE as they interact with an electric field

17
Q

How are ions detected?

A

flow onto a negatively charged detector/plate, causing a current. Higher abundance= greater current

18
Q

How can the Ar be calculated using mass spectra?

A

Ar = m/z x abundance (repeated if more than one peak) / total abundance

19
Q

Why do successive I.Es often require more energy?

A

as the electron is being removed from a positively charged ion, so electrostatic attraction is stronger

20
Q

Why is the 3rd I.E of Mg much higher than the 2nd I.E of Mg?

A
  • electron removed is from the 2p sub-shell
  • so the electron being removed is less shielded