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Chemistry > Atomic Structure > Flashcards

Atomic Structure Flashcards

1
Q

State the definition of relative atomic mass?

A

The average mass of an atom of an element on a scale when carbon-12 is exactly 12 (comparison).

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2
Q

State the definition of relative isotopic mass?

A

The mass of an atom of an isotope of an element on a scale where carbon-12 is exactly 12 (comparison)

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3
Q

State the definition of relative molecular mass?

simple organic molecules

A

Mr is the average mass of a molecule on scale where an atom of carbon-12 is exactly 12.

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4
Q

State the definition of relative formula mass?

used for inorganic substances

A

Average mass of a formula unit on a scale where an atom of carbon-12 is exactly.

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5
Q

State particles masses and charges?

A

proton — 1 — +1
neutrons — 1 — 0
electrons — 1/2000 — -1

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6
Q

Explain basics of ions?

A

gaining electrons - anion (-ide) - negative charge
group 6 - gains 2 electrons
group 7 - gains 1 electron

losing electrons - cations - positive charge
group 1 - loses 1 electron
group 2 - gains 2 electrons

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7
Q

Explain isotopes?

A

They have the same number of protons but different numbers of nuetrons - SAME ELEMENT

All elements exists in isotopic forms - what varies in abundance of each one.

CHEMICAL ACTIVITY IS DETERMINED BY ELECTRONS

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8
Q

Describe John Dalton’s theory?

A
  • defined what an element is
  • solid sphere
  • different atoms have different spheres
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9
Q

Describe JJ Thomson’s theory?

A

-presence of electrons embedded in sphere,

plum pudding

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10
Q

Describe Ernest Rutherford’s theory?

A
  • carried out gold thin foil experiment which was few atoms thick
  • used alpha particles (helium positive nucleus)
  • if plum pudding model was correct then most particles would be deflected
  • 97% of particles went through, some were deflected and others bounced at an angle
  • this proved atoms were mostly empty space because electron repelled by positive nucleus
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11
Q

Describe Neils Bohr’s theory?

A
  • thought if electrons are negative and nucleus is positive, what is stopping atom from falling into nucleus
  • discovered electrons exist in fixed orbits/energy levels with a fixed energy
  • electrons can move between shells with an energy change

-particular energy linked to particular wavelength linked to different colours due to electrons jumping shells and releasing specific amounts of energy.

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12
Q

What is mass spectometery?

A

A machine (chemical analysis) used in

  • identify elements
  • relative atomic mass
  • relative abundance of isotopes
  • relative molecular mass of molecule.
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13
Q

What are the five stages of mass spectrometery?

A
  1. Ionisation
  2. Acceleration
  3. Ion drift
  4. Data detection
  5. Data analysis
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14
Q

Main equations in mass spectrometery?

A
  • KE = 1/2mv^2
  • v = d/t
  • v = square root 2ke/m
  • d/t = square root 2ke/m
  • d = t x square root 2ke/m
  • t = d/square root 2ke/m
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15
Q

Explain general ionisation?

A

The aim is to create particles with a positive charge for the subsequent stages to work. 2 methods!
Any substance in a spectrometry put in bracket and a plus charge to be affected by magnetic fields.

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16
Q

Explain electrospray ionisation?

A
  • sample is dissolved in a solvent
  • pushed through a nozzle at a huge pressure
  • voltage applied so each particle gains a H+ ion (protons)
17
Q

Explain electron impact ionisation?

A
  • sample is vapourised
  • an electron gun fires high energy electrons at the sample
  • this knocks off at least one electron of each particle so it gains a positive charge
18
Q

Describe what happens in accelerations?

A
  • the aim is to give all particles the same amount of energy
  • they then will move at different speeds depending on their mass
  • an electric field causes the now positive charge particle to accelerate
  • lighter ions experiences greater acceleration
  • heavier ions experience less acceleration
    (due to mass of each ion)
19
Q

Describe what happens in ion drift?

A
  • the drift is important in separating the ions because if they moved at the same speed they would be detected at the same time
  • they need to drift apart to record the time of flight
  • this region has no electric field so lighter ions travel faster and heavier ions drift slower so therefore take less time to reach the detector
20
Q

Describe what happens in data detection?

A
  • recording what has travelled across machine
  • when a positive charge hits the detector and create a small current
  • detector records how long it took for that particle to generate that current
  • large current means more particles with that particular mass
  • overall data is used to calculate the mass/charge for each particle (mass/charge = m/e - charge normally 1)
21
Q

Describe what happens in data analysis?

A
  • this is about recording what has travelled across the machine
  • a mass spectrum is a type of chart produced from information from the detector records
  • y axis % abundance
  • x axis mass charge ratio
22
Q

Explain how to analyse compounds?

A
  • compounds appear as peaks on a mass spectrometery graph
  • the could be extra peaks due to fragmentations which is when ionised molecules break apart
  • base peak is highest peak, most abundant
  • molecular ion peak is the major peak m/e is Mr
  • M +1 peak is sometimes a small extra peak due to naturally occurring isotope
23
Q

What are energy levels?

A
  • electrons exist at orbital which exists in a principle energy level
  • this principle energy level is given a number from lowest in energy (closest to nucleus) each principle energy level contains more electrons the higher you get in energy
24
Q

Describe the type of orbitals?

A

1 type - S orbital

3 types - P orbital (px,py,pz)

5 types - D orbital

7 types - F orbitals

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

25
Q

Explain why you can’t work out positions of electrons?

A
  • not all electrons are identical in energy so it’s impossible to work out where an electron is but we can indicate a region (orbital) of space where it’s likely to be
26
Q

State the definition of first ionisation energy?

A

The first ionisation energy is the energy required to remove on electron from each atom in 1 mole of gaseous atom to form 1 mole made of gaseous 1+ ion.

E.G. Mg(g) - Mg+(g) + e-

27
Q

Why must it be gaseous atoms/ions?

A
  • you use energy to turn it into a gas but you only want energy which represents removal of electrons.
28
Q

State basic facts about ionisation energy?

A
  • endothermic reaction
  • energy change is always positive
  • always refer as 1 mole not atoms/ions
  • bigger the value more difficult it is to remove energy as they are held tighter due to strong attraction
  • letting an electron go requires energy
  • letting an electron in releases energy
29
Q

How does the nuclear charge affect ionisation energy?

A

nuclear charge = more protons in nucleus = greater positive charge = greater attraction for electrons = more energy needed to remove them

30
Q

How does the distance from nucleus affect ionisation energy?

A

the further the distance from nucleus the attraction from nucleus drops as electrons get further away

31
Q

How does shielding affect ionisation energy?

A

full energy levels of electrons will repel outer electrons making it easier to remove them.
MOST IMPORTANT FACTOR!

32
Q

State the definitions of second ionisation energy?

A

The second ionisation energy is the energy required to remove 1 electron from each ion in 1 mole of gaseous 1+ ion to form 1+ mole of gaseous 2+ ions.
E.G. Mg+ (g) - Mg2+ (g) + e-

33
Q

Explain the trend in ionisation energy when going down a group?

A

Ionisation energy generally decreases as outer electrons get further away from the nucleus and there is significant increase in shielding despite increasing nuclear charge.

34
Q

Explain the trend in ionisation energy when going across a period?

A

Ionisation energy generally increase due to increased nuclear charge but no significant change in shielding or distance from nucleus.

35
Q

Why is group 2+3 an exception?

A

Outer electron is in a P orbital so it is slightly shielded by complete S orbital reducing ionisation energy.

36
Q

Why is group 5+6 an exception?

A

Outer electrons are being paired in a P orbital so mutual repulsion occurs making it easier to remove electrons.

Chemistry (5 decks)

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