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Physical Chemistry > Section 1.1- Atomic Structure > Flashcards

Section 1.1- Atomic Structure Flashcards

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1
Q

What letter is used to represent the atomic number of an atom?

A

Z

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2
Q

What does the atomic number tell us about an element?

A

atomic number = number of protons in an atom

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3
Q

What letter represents mass number?

A

A

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4
Q

How is the mass number calculated?

A

number of protons + number of neutrons

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5
Q

Define relative atomic mass

A

mean average mass of all atoms of an element (taking isotopes into account) relative to 1/12 mass of an atom of carbon12

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6
Q

What are isotopes of an element?

A
  • different forms of the same element
  • have the same number of protons (and electrons) but a different number of neutrons
  • they still have the same chemical properties
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7
Q

What is the mass of a proton?

A

1

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8
Q

What is the charge of a proton?

A

+1

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9
Q

What is the mass of a neutron?

A

1

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10
Q

What is the charge of a neutron?

A

0 (no charge)

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11
Q

What is the mass of an electron?

A

0 (negligible)

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12
Q

What is the charge of an electron?

A

-1

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13
Q

define ionisation

A

process in which atoms lose or gain electrons and become ions
- cations (+)
- anions (-)

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14
Q

Define 1st ionisation energy

A

the energy required to remove one electron from one mole of gaseous atoms to form one mole of gaseous 1+ ions

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15
Q

1st ionisation energy general formula

A

M(g) = M+(g) + e-(g)

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16
Q

2nd ionisation energy general formula

A

M+(g) = M2+(g) + e-(g)

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17
Q

Trends in ionisation energies:
- ionisation energy as more electrons are removed

A
  • more electrons removed = successive ionisation energy increases
    -more significant jumps in ionisation energy where electrons are being removed from the next principle energy level ( as electrons are closer to the nucleus on nearer electron shells so are held more tightly)
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18
Q

Trends in ionisation energies:
group 2 elements and 1st ionisation energy

A
  • nuclear charge increases down group 2 but the 1st ionisation energy decreases
  • this means electrons are being removed from successively higher energy levels, which lie further from the nucleus and so are less attracted to the nucleus
  • outer electrons also ‘shielded’ from nuclear pull by inner shells
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19
Q

Trends in ionisation energies
going along a period and ionisation energy (overall trend)

A
  • as you go along a period (L-R), the 1st ionisation energy increases
  • this is because as you go along a period, the number of protons in the nucleus increases so the attraction between the nucleus and outer electrons increases
  • therefore amount of energy needed to remove an electron increases
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20
Q

Why are all ionisation energies endothermic?

A
  • endothermic = positive energy changes and require energy
  • endothermic as energy is needed to overcome the electrostatic attraction between electron + nucleus
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21
Q

what is an electron shell known as?

A

principle energy level

22
Q

Max number of electrons for sublevel S

A

2

23
Q

Max number of electrons for sublevel P

A

6

24
Q

Max number of electrons for sublevel D

A

10

25
Q

Max number of electrons for sublevel F

A

14

26
Q

1st principle energy level:
- sub levels
-max number of electrons

A
  • sublevels: 1S
  • max number of electrons: 2
27
Q

2nd principle energy level:
- sub levels
-max number of electrons

A
  • sublevels: 2S, 2P
  • max number of electrons: 8
28
Q

3rd principle energy level:
- sub levels
-max number of electrons

A
  • sublevels: 3S, 3P, 3D
  • max number of electrons: 18
29
Q

4th principle energy level:
- sub levels
-max number of electrons

A
  • sublevels: 4S, 4P, 4D, 4F
  • max number of electrons: 32
30
Q

What does the Aufbau principle state?

A

lowest energy sublevels are occupied 1st

31
Q

Sub levels (increasing energy)

A

1S, 2S, 2P, 3S, 3P, 4S, 3D, 4P
- positive ions lose electrons from 4S before 3D

32
Q

What is an orbital?

A

a region around the nucleus than can hold up to two electrons

33
Q

P sublevel
-number of orbits
-max number of electrons

A

-number of orbits: 3
- max number of electrons: 6

34
Q

S sublevel
-number of orbits
-max number of electrons

A

-number of orbits: 1
- max number of electrons: 2

35
Q

D sublevel
-number of orbits
-max number of electrons

A

-number of orbits: 5
- max number of electrons: 10

36
Q

F sublevel
-number of orbits
-max number of electrons

A

-number of orbits: 7
- max number of electrons: 14

37
Q

How many electrons can an orbital contain?

A

no more than 2 electrons (Pauli exclusion principle)

38
Q

What would the relationship between 2 electrons in the same orbital in terms of their spin be?

A

have opposite spin as they repel each other as they are both negative

39
Q

Hund’s rule

A

single electrons must occupy all empty orbitals within a sublevel before they start to form pairs in orbitals

40
Q

Exceptions: Chromium

A
  • Only has one electron in its 4S orbital before filling 3D
    1S(2)…3P(6), 4S(1), 3D(5)
41
Q

Exceptions: Copper

A
  • only has one electron in its 4S orbital before filling 3D
    -1S(2)…3P(6), 4S(1), 3D(10)
42
Q

Time of flight mass spectrometer
- order

A
  • ionisation area
  • acceleration area
  • flight path (ion drift)
  • ion detector
43
Q

Time of flight mass spectrometer
- ionisation area method 1

A

Electrospray:
sample dissolved in volatile solvent e.g. water/methanol and injected through a fine hypodermic needle to give an aerosol. needle attached to positive terminal of a high voltage power supply and particles gain a proton from the solvent as they leave the needle, producing XH+ ions (+1 charge and mass of Mr +1) (ions rarely fragment)
X(g) + solvent -H = XH+(g) + solvent-
(solvent- evaporates)

44
Q

Time of flight mass spectrometer
- ionisation area method 2

A

Electron bombardment/impact:
normally sample is initially vaporised
electron gun (hot wire filament with current through it emitting high speed electrons) knocks of one electron from each particle to form 1+ molecular ions (these ions fragment)
X(g) + e- = X+(g) +2e-

45
Q

When would you use electron impact/bombardment for ionisation in a mass spectrometer?

A

for organic or inorganic molecules with a low formula mass

46
Q

When would you use electrospray for ionisation in a mass spectrometer?

A

for substances with a higher molecular mass including biological molecules e.g. proteins

47
Q

Time of flight mass spectrometer
-acceleration

A

positive ions attracted towards a negatively charged plate. electric field is applied to the ions. each ion receives the same amount of kinetic energy. ions with a lower mass/charge ratio accelerate more quickly so ions with a lower mass experience greater acceleration

48
Q

Time of flight mass spectrometer
- ion drift

A

ions pass through hole in the plate to the flight chamber, they drift through at constant velocity. ions form a beam with constant kinetic energy, travel along tube to detector. time of flight is therefore directly proportional to the square root of mass. ions with less mass (lower mas/charge ratio) pass through most quickly

49
Q

Time of flight mass spectrometer
-detection

A

positive ions pick up electrons, current flows (size of current depends on number of ions arriving), m/z value and time of flight recorded. largest current from most abundant ions

50
Q

How to find relative atomic mass

A

(abundance *relative mass of isotope) /100

Physical Chemistry (3 decks)

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