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Chemistry > 1.1 Atomic Structure > Flashcards

1.1 Atomic Structure Flashcards

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1
Q

Atomic number

A

Number of protons in the nucleus of an atom

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2
Q

Mass number

A

Number of protons and neutrons in the nucleus of an atom

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3
Q

Isotopes

A

Atoms of the same element (same number of protons) with a different number of neutrons

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4
Q

What is a mass spectrometer used for?

A

Calculating the relative atomic mass of an element or the relative molecular mass of a compound.

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5
Q

What are the 4 stages of a TOF mass spectrometer?

A
  • Ionisation
  • Acceleration
  • Separation of ions
  • Detection
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6
Q

Why is the spectrometer kept in a vacuum?

A

To prevent ions that are made from colliding with molecules in the air.

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7
Q

Mass spectrometer
What are the two methods of ionisation?

A
  • Electron impact
  • Electrospray ionisation
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8
Q

Mass spectrometer
How does electron impact ionisation work?

A
  • Sample is vapourised and injected into spectrometer
  • High energy electrons fired from an electron gun
  • Electron is knocked from each particle
  • Positive ions formed
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9
Q

Mass spectrometer
What is an electron gun?

A

A hot wire filament that releases high energy electrons.

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10
Q

Mass spectrometer
What is the charge of the ions formed?

A

1+

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11
Q

Mass spectrometer
How are the positive ions accelerated?

A

With an electric field

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12
Q

Mass spectrometer
How are the ions separated?

A

Lighter ions travel through the spectrometer faster than heavier ions

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13
Q

Mass spectrometer
How are the ions detected?

A

Each ion gains an electron - this generates a current

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14
Q

Mass spectrometer
How is the abundance of each ion determined?

A

It is proportional to the current produced.
The greater the abundance, the greater the current.

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15
Q

Mass spectrometer
Why is the sample ionised?

A

So it can be accelerated and detected

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16
Q

Relative isotopic mass

A

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

17
Q

Relative atomic mass (Ar)

A

Weighted average mass of all isotopes of an element / 1/12 mass of one atom of carbon-12

18
Q

What order do the energy levels fill up?

A

1s–>2s–>2p–>3s–>3p–>4s–>3d–>4p

19
Q

Electron configuration for chromium (Cr)?

A

1s²2s²2p⁶3s²3p⁶3d⁵4s¹

20
Q

Electron configuration for copper (Cu)?

A

1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹

21
Q

(First) Ionisation energy

A

The energy needed to remove one mole of electrons from one mole of atoms in the gaseous state.

22
Q

Why do successive ionisation energies increase?

A
  • Attraction of the outer electrons and nucleus increases (same number of protons for fewer electrons)
  • Large increase where outer electron is in a new main shell (closer to nucleus with less shielding)
23
Q

Which shell are electrons lost from first in period 4 transition metals?

A

4s

24
Q

Mass spectrometer
How does electrospray ionisation work?

A
  • Sample dissolved in a volatile polar solvent
  • Injected through a hypodermic needle which gives a fine mist
  • Tip of needle is attached to positive terminal of a high voltage supply
  • Particles gain a protons from the solvent
25
Q

What is a polar solvent?

A

A solvent with molecules with an area of more positive charge and an area of more negative charge.

26
Q

Volatile

A

Easy to turn into a vapour

27
Q

Why is a volatile solvent used for electrospray ionisation?

A

So that all of it evaporates leaving only the positive ions of the sample

28
Q

What is the mass of the ion formed with electrospray ionisation?

A

Mass of ion = mass of element/compound + 1

29
Q

What is the mass of the ion formed with electron impact ionisation?

A

Mass of ion = mass of element/compound

30
Q

m/z

A

Mass/charge
(Z is usually +1 so x-axis is relative isotopic mass)

31
Q

What are the units of ionisation energy?

A

KJ mol⁻¹

Chemistry (8 decks)

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