1.1 Atomic Structure (part 1) Flashcards Preview

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Flashcards in 1.1 Atomic Structure (part 1) Deck (42)
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1
Q

What subatomic particles are atoms made up of

A

Protons, neutrons and electrons

2
Q

What is the charge, mass and location of a proton?

A

Charge: +1
Mass: 1
Location: nucleus

3
Q

What is the charge, mass and location of a neutron?

A

Mass: 1
Charge: 0
Location: nucleus

4
Q

What is the charge, mass and location of an electron?

A

Mass: 1/2000
Charge: -1
Location: shells

5
Q

Atomic number definition

A

Number of protons in the nucleus of an atom

6
Q

Mass number definition

A

Number of protons and neutrons in the nucleus of an atom

7
Q

Isotope

A

Atoms of the same element with a different number of neutrons

8
Q

Why do isotopes have the same chemical properties?

A

Same no of elections> same electron configuration> dictates chemical behaviour

9
Q

What is formed when an atom loses electrons

A

Positively charged ion (cation)

10
Q

What is formed what an atom gains electrons?

A

A negative ion (anion)

11
Q

What is mass spectrometry used for?

A

Determining information about elements and compounds, it can be used to calculate relative atomic mass of an electrons or relative molecular mass of a compound

12
Q

What are the four stages of mass spectrometry

A
  • ionisation
  • acceleration
  • separation of ions
  • detection
13
Q

What two methods of ionisation are there

A

Electron impact and electrospray ionisation

14
Q

What are the 3 stages of electron impact ionisation

A
  • sample injected into spectrometer and vaporised
  • high energy electrons from electron gun fired at sample
  • high energy electrons knock off an electron from each particle to form positive ions
15
Q

What would the equation be if gaseous sodium was ionised by electron impact ionisation

A

Na (g) -> Na+ + e-

16
Q

What are the 4 stages of electrospray ionisation?

A
  • sample dissolved in polar solvent
  • injected through a fine hypodermic needle to give a fine mist
  • tip of needle is attached to the positive terminal of a high voltage supply
  • particles gain a proton (H+ ion) from the solvent to form positive ions
17
Q

What would the equation by if methane was ionised by electrospray ionisation

A

CH4 + H+ -> CH5+

18
Q

What is the mass of the ion after electron impact ionisation

A

Mass of ion= mass of element/compound

19
Q

What would the mass of an ion be if it was ionised by electrospray ionisation?

A

Mass of ion = mass of element/compound +1

20
Q

What happens in acceleration?

A

An electric field is applied to accelerate the positive ions. This gives all the ions with the same charge the same kinetic energy

21
Q

Do lighter or heavier ions travel faster

A

Lighter

22
Q

What happens in seperation?

A

Lighter ions reach the detector first

Heavier ions reach the detector last

23
Q

Why is the spectrometer kept under a vacuum?

A

To prevent other molecules in air colliding with the sample ions

24
Q

What does a detector do

A

Records the different ions as they arrive at the detector

25
Q

Why can ions be detected

A

They gain an electron at the detector to produce a current. The more ions of one type, the greater the current and bigger the peak

26
Q

How is mass spectra plotted

A

Relative abundance against mass to charge ratio

27
Q

Why is there never a peak at the relative atomic mass of an isotopic element?

A

The relative atomic mass is an average

28
Q

Why must the sample be ionised?

A

So it can be accelerated and detected

29
Q

Isotopic mass

A

The mass of an isotope relative to 1/12th the mass of an atom of carbon 12

30
Q

Relative atomic mass

A

Weighted average mass of all the isotopes relative to 1/12th the mass of a carbon-12 atom

31
Q

How to calculate the relative atomic mass

A

(Massxabundance of each isotope)/total abundance

32
Q

How to calculate the relative atomic mass from mass spectra

A

Multiple each m/z by relative abundance and add them up, divide the whole thing by 100

33
Q

What is molecular ion peak of CH3OH (electron impact)

A

M/z = 32 (CH3OH+)

34
Q

Why would there be a peak at 33 in methanol (electron impact)

A

Small amount of carbon 13 present

35
Q

Why would there be peaks below 32 in methanol (electron impact)

A

Molecule fragments until electron impact

36
Q

Which peak in mass spectra shows the complete molecule (electron impact ionisation)

A

The peak furthest to the right

37
Q

How does mass spectra from electrospray ionisation differ from electron impact

A

Does not cause fragmentation of the molecular ion so fewer peaks are present

38
Q

Why would there be a peak at m/z 265 C12H24O6 (electrospray)

A

Gains hydrogen ion

C12H25O6+

39
Q

Why would there be a peak at m/z 266 in mass spectra for C12H24O6 (electrospray)

A

Carbon 13= C13H25O6

40
Q

Why would there be no peaks below 265 in mass spectra of C12H24O6 (electrospray)

A

No fragmentation

41
Q

Ion in electron impact

A

M+

42
Q

Ion in electrospray ionisation

A

MH+