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CHEMISTRY (AS) > Atomic Structure > Flashcards

Atomic Structure Flashcards

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1
Q

What are the relative mass and relative charge of protons, neutrons and electrons?

A

Relative mass: Relative charge:
P: 1 P: +1
N: 1 N: 0
E :Negligible E: -1

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2
Q

What is the structure of the atom?

A

Have a -1 charge
Whizz around nucleus in orbitals that take up most of vol
Most of mass is conc in nucleus
Mass + charge of subatomic particles in nucleus are v. small so relative m + c used instead

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3
Q

What is the mass number?

A

Total no. of P + N + E in an atom

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4
Q

What is the Atomic (proton) number?

A

The no. of protons in nucleus of atom that identifies element.
All atoms of same element have same no. of protons.

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5
Q

What are ions?

A

Atoms form ions by gaining/losing electrons.
They have diff… no. of P + E
They have a - or + next to them

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6
Q

What are isotopes?

A

Atoms with the same no. of protons but different number of neutrons
Show isotope of Mg as: Magnesium-24, 24Mg or 24,12Mg

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7
Q

What decides the chemical properties of an element?

A

The no. + arrangment of electrons.

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8
Q

Do isotopes have the same chemical + physical properties?

A

Chemical: Yes-They have the same elec… configuration
Physical: No-Slightly diff… as this tends to depend more on mass of atom

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9
Q
  1. What did John ______ describe atoms to be?
  2. What did J.J. _______ conclude from his experiments in
    18__?
A
  1. Solid spheres + diff… spheres made up diff… elements.
  2. Atom must contain even smaller, -vely charged particles
    (elec. ..). New model (Plum Pudding model)
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10
Q

Explain Ernest Rutherford’s model in 1909?

A

Him + his students Hans Geiger + Ernest Marsden conducted the famous gold foil experiment.
+vely charge alpha particles were fired at v. thin sheet of gold.
From plum pudding they expected most of alpha particles to be deflected slightly by +ve ‘pudding’ that made most of atom.
Most passed straight through + v. small no. deflected backwards.
So he came up with nuclear model-There’s tiny +vely charged nucleus in centre, surrounded by ‘cloud’ of -ve elec…most is empty space.

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11
Q

What did Neil Bohr’s model conclude?

A

Scientists realised if elec… were in ‘cloud’ around nucleus of atom + quickly spiral down into nucelus causing atom to collapse. New model:
1) Elec… only exists in fixed orbits (shells) + not anywhere
in between.
2) Each shell has a fixed energy
3) When an elec… moves between shells electromagnetic
radiation is emitted/absorbed.
4) Because energy of shells is fixed, radiation will have a
fixed frequency.

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12
Q

Define Relative Atomic Mass?

A

Ar is average mass of an atom of an element on a scale where an atom of carbon-12 is exactly 12. Ar of elements shown on periodic table.

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13
Q

Define Relative Isotopic Mass?

A

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

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14
Q

How do you calculate RAM?

A

Usually whole no (an average).

RAM=(isotopic masses x percentages) / total percentage

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15
Q

Define Relative Molecular Mass?

A

Mr is average mass of a molecule on a scale where one atom of carbon-12 is exactly 12.
Mr=Ar of each atom x no. of that atom

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16
Q

Define Relative Molecular Mass?

A

Mr is average mass of a molecule on a scale where one atom of carbon-12 is exactly 12.
Mr=Ar of each atom x no. of that atom

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17
Q

Define Relative Formula Mass?

A

The average mass of a formula unit on a scale where an atom of carbon-12 is exactly 12. Used for ionic compounds.

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18
Q

How do you find Relative Formula Mass?

A

Add all of all ions in the formula unit.

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19
Q

What is a mass spectrometer?

A

Machine which can be used to analyse elements + compounds. Can give u info: 1) Relative molecular mass
2) Relative abundance of isotopes

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20
Q

Explain the 4 main things that happen when a sample s squirted into a TOF mass spectrometer?

A
  1. Electrospray ionisation:
    Sample is dissolved in polar solvent.
    Pushed through small nozzle at high pressure.
    High voltage applies causing particles to lose elec…
    Ionised particles are separated from solvent leaving gas made up of +ve ions
  2. Acceleration:
    +ve ions are accelerated by electric field.
    Particles need to be +vely charged to be accelerated.
    Elec… field gives same KE to all ions.
    Ions with lower mass/charge experience greater acceleration.
    They’re given as much energy as heavier ions but they’re lighter so experience more aceleration
  3. Ion drift
    Ions leave electric field with constant speed + KE.
    They enter region with no electric field + drift through it same speed they left electric field.
    Ions with lower mass/charge ratios will be drifting at higher speeds.
  4. Detection
    Because ions with lower mass/charge ratio travel through drift region at higher speeds, they reach detector in less time than ions with higher mass/charge ratio.
    Detector detects current created when ions hits it and records how long it took for them to pass through mass spectrometer.
    This data then used to calc… mass/charge values needed to produce a mass spectrum.
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21
Q

Why would the particles need to be ionised when they’re put in the mass spectrometer?

A

If they weren’t, they couldn’t be accelerated by the electric field or detected by the ion detector.

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22
Q

What is a mass spectrum?

A

A type of chart produced by a mass spectrometer.

It shows information about the sample that was passed through the mass spectrometer.

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23
Q

What does a mass spectrum look like and what do the different components represent?

A

If sample is an element.

1) Lines-represent a diff… isotope of element
2) y-axis- abundance of ions (often as %)
3) Height of each peak-is relative isotopic abundance.
4) X-axis-Units given as mass/charge ratio.

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24
Q

What can you assume about the x-axis since the charge on most ions is +1?

A

That the x-axis is simply the relative isotopic abundance.

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25
Q

What is Mass/charge often shown as?

A

m/z

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26
Q

TRUE or FALSE: The ions produced by the mass spectrometer are always positive? Why.

A

TRUE: The mass spectrometer produces ions by removing an elec… so ions produced are always +ve even for substances like Cl (normally form -ve ions)

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27
Q

Why do elements with different isotopes produce more than one line in a mass spectrum?

A

Because the isotopes have different masses.

This produces characteristic patterns which can be used as ‘fingerprints’ to identify certain elements.

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28
Q

Many elements only have one stable isotope.

How can they be identified in a mass spectrum?

A

By looking for a line at their relative atomic masses.

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29
Q

How do you calculate the Relative Atomic Mass (Ar) of an element from a mass spectrum?

A

Step 1: For each peak, read the % relative isotopic abundance from y-axis + the relative isotopic mass from
x-axis. Multiply them together to get total relative mass for each isotope.
Step 2: Add up these totals
Step 3: Divide by 100 (since %es were used)

30
Q

What do you do if the relative abundance is not given as a percentage?

A

Just do steps 1 and 2 but then divide by total relative abundance instead.

31
Q

How do you find total relative abundance?

A

Add up relative abundances of all the isotopes in the sample.

32
Q

You can also get a mass spectrum for a molecular sample. A molecular ion M+(g) is formed when 1 elec… is removed from the molecule.
What is shown on the mass spectrum for this?

A

This gives a peak in the spectrum with a mass/charge ratio equal to the Mr of molecule.
Can be used to help identify an unknown compound.

33
Q

What will be produced on the mass spectra if you have a mixture of compounds?

A

They’ll have diff… Mr values so you’ll get a peak for the molecular ion of each one.

34
Q

Electrons have have fixed energies that move around the nucleus in certain regions of the atom called…

A

…shells or energy levels.

35
Q

What is the number each shell is given?

A

The principle quantum number.
(The further shell is from nucleus, the higher its energy + the larger its PQ no.)
e.g. 1st elec… shell, PQ no.= 1 , shell has lowest energy
3rd elec… shell, PQ no.= 3 , shell has highest energy

36
Q

What do experiments show about electrons in a shell?

A

They don’t all have exactly the same energy.

37
Q

What are shells divided up into?

A

Sub-shells-different electron shells have different numbers of sub-shells, which each have a diff… energy.
s sub-shells, p sub-shells, d sub-shells or f sub-shells

38
Q

What sub shells do each shells contain?

A

1st shell: 1s
2nd shell: 2s, 2p
3rd shell: 3s, 3p, 3d
4th shell: 4s, 4p, 4d, 4f

39
Q

Explain what the notation of ‘3p’ represents?

A

The number shows what shell its in.
The letter shows what type of sub-shell it is.
So 3p means a p sub-shell in the 3rd electron shell.

40
Q

The sub-shells have different numbers of orbitals.

How many electrons can each orbitals hold?

A

2 electrons.

41
Q

How many orbitals and electrons do each sub-shells have?

A

s: 1 orbital 1 x 2 = 2e
p: 3 orbitals 3 x 2 = 6e
d: 5 orbitals 5 x 2 = 10e
f: 7 orbitals 7 x 2 = 14e

42
Q

How many electrons can the first 4 electron shells hold?

A

Shell: Sub-shell: Total no. of elec…

1st: 1s 2 = 2
2nd: 2s, 2p 2 + (3 x 2) = 8
3rd: 3s, 3p, 3d 2 + (3 x 2) + (5 x 2) = 18
4th: 4s, 4p, 4d, 4f 2 + (3 x 2) + (5 x 2) + (7 x 2) = 32

43
Q

Define electron configuration?

A

The no. of elec… that an atom or ion has + how they’re arranged.

44
Q

Explain the 3 different ways electron configuration can be shown?

A
  1. Sub-shell notation:
    1s2, 2s2, 2p6 (number=PQ no. , letter=sub-shell ,
    small number=no. of elec…)
  2. Arrows in boxes:
    Each box represents one orbital + each arrow represents one elec… The up + down arrow represents elec… spinning in opposite directions. 2 elec… can only occupy same orbital if they have opposite spin.
  3. Energy level diagrams:
    These show energy of elec… in diff… orbitals as well as the no. of elec… and their arrangement.
45
Q

How can you work out electron configurations?

A

RULE 1:
Elec… fill up the lowest energy sub-shells first (except the 4s sub-shell which has a lower energy level than 3d sub-shell even though it has a higher PQ no. meaning the 4s sub-shell fills up first).
RULE 2:
Electrons fill orbitals in a sub-shell singly before they start sharing.
RULE 3:
For the configuration of ions from the s + p blocks of the periodic table, just add or remove elec… to or from the highest energy occupied sub-shell.

46
Q

How would you write the shortened electron configurations?

A

Noble gas symbols in the square brackets e.g. [Ar] 4s2 for Calcium.

47
Q

Which way of showing electron configuration should you use if asked in an exam?

A

Sub-shell notation

48
Q

If asked to give the full electron configuration in an exam, what should you do?

A

Write out full sub-shell notation (not noble gas shorthand)

49
Q

Which 2 transition elements don’t follow the normal rules for electron configurations?

A

Chromium (Cr) + Copper (Cu)`

50
Q

Why are Cr and Cu badly behaved?

A

They donate one of their 4s elec… to the 3d sub-shell.

They’re happier with a more stable full or half-full d sub-shell.

51
Q

What is the electron configuration of the Cr atom?

A

1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1

not ending in 3d4, 4s2 as you’d expect

52
Q

What is the electron configuration of the Cu atom?

A

1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1

not ending in 3d9, 4s2 as you’d expect

53
Q

What happens to transition metal’s electron configuration when they become ions?

A

They lose their 4s electrons before their 3d electrons.
e.g. Fe3+ loses 3 elec… 2 4s elec… + 1 3d elec…
Fe3+ ion: 1s2, 2s2, 2p6, 3s2, 3p6, 3d5

54
Q

What is the relationship between electronic structure and chemical properties?

A

The no. of outer shell elec… decides the chemical properties of an element.
Group 1 + 2 easily lose elec… to form +ve ions with inert gas configuration.
Group 5, 6 + 7 gain elec… to form -ve ions with an inert
gas configuration.
4 to 7 can also share elec… when forming covalent bonds.
Group 0 have completely filled s + p sub-shells + don’t need to gain/lose/share elec… full shells make them inert.

55
Q

Define first ionisation energy?

A

The energy needed to remove 1 elec… from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

56
Q

Write out the equation for the first ionisation energy of oxygen?

A

O(g)—->O+(g) + e-

57
Q

What are 3 important things to remember about ionisation energies?

A
  1. You must use the gas symbol, (g), because ionisation energies are measured for gaseous atoms.
  2. Always refer to 1 mole of atoms, as stated in definition, rather than single atom.
  3. The lower the ionisation energy, the easier it is to form a +ve ion.
58
Q

What can ionisation energy also be referred to as?

A

Ionisation enthalpy

59
Q

What does high ionisation energy mean?

A

There’s a high attraction between the electron + the nucleus so more energy is needed to remove elec…

60
Q

What are the 3 main factors affecting ionisation energies?

A
  1. Nuclear charge:
    The more protons there are in nucleus, the more +vely charged nucleus + the stronger the attraction for the elec…
  2. Distance from nucleus:
    Attraction falls v. rapidly with distance. An elec… close ro nucleus will be much more attracted than one further away.
  3. Shielding:
    As no. of elec… between outer elec… + nucleus increases, the outer elec… feel less of an attraction to nucleus. Lessening of pull of the nucleus thanks to inner elec… shells is called shielding.
61
Q

Is ionisation an endothermic or exothermic process?

A

ENDOTHERMIC because you have to put energy in to remove an elec… from an atom/molecule.

62
Q

When can you usually see the effect of nuclear charge on ionisation energy?

A

When you compare atoms with outer elec… the same distance from the nucleus and with equal shielding effects.
1. Usually with elements that are in the same period of the periodic table.

63
Q

Define 2nd ionisation energy?

A

The energy needed to remove an elec… from each ion in 1 mole of gaseous 1+ ions.
e.g. O+(g)—>O2+(g) + e-

64
Q

Why are 2nd ionisation energies greater than 1st ionisation energies?

A

Because the elec… is being removed from a +ve ion (not atom) which will require more energy.
Elec… configuration will play role in how much larger 2nd ionisation energy is than 1st.

65
Q

Define successive ionisation energy?

A

You can remove all the elec… from an atom leaving only the nucleus. Each time you remove an elec… there’s a successive ionisation energy.

66
Q

You need to be able to write equations for any successive ionisation.
What is the general equation for the nth ionisation?

A

X(n-1)+(g) —> Xn+(g) + e-
e.g. the 5th ionisation of oxygen is:
O4+(g) —> O5+(g) + e-

67
Q

What are the ionisation trends down group 2?

A

The first ionisation energy decreases down group 2.
Provides evidence for the existence of elec… shells.
If each element going down group 2 has one more elec… shell than the one above, the extra shell will shield the outer elec… from the attraction of the nucleus.
Extra shell also means outer elec… will be further from the nucleus so nucleus’s attraction will be reduced.
Both factors make it easier to remove outer elec… resulting in lower ionisation energies.

68
Q

What is the ionisation trends across periods?

e.g. Group 3

A

As you move across a period, general trend is for ionisation energies to increase.
The no. of protons is increasing so stronger nuclear attraction.
All extra elec…are at roughly same energy level even if outer elec… are in diff… orbital types.
So generally little shielding effect or extra distance to lessen attraction from the nucleus.

69
Q

Why are there small drops on the graph between Groups 2 and 3 and what do they show?

A

They show sub-shell structure.
Mg: 1s2, 2s2, 2p6, 3s2 Al: 1s2, 2s2, 2p6, 3s2, 3p1
Al outer elec… is in 3p orbital rather than 3s + 3p orbital has slightly higher energy than 3s orbital so electron on average to be found further from nucleus.
3p orbital has additional shielding provided by 3s elec…s.
2 factors strong enough to override effect of increased nuclear charge, resulting in the ionisation dropping slightly. Pattern in ionisation energies provides evidence for theory of elec… sub-shell structure.

70
Q

Why are there small drops on the graph between Groups 5 and 6 and what do they show?

A

Due to elec… repulsion.
P: 1s2, 2s2, 2p6, 3s2, 3p3 S: 1s2, 2s2, 2p6, 3s2, 3p4
Shielding is identical in P + S atoms + elec… is being removed from an identical orbital.
In P’s case, elec… is being removed from a singly-occupied orbital. But for S, the elec… is being removed from orbital containing 2 elec… Repulsion between 2 elec… in an orbital means elec… are easier to remove from shared orbitals.

71
Q

What can knowing the successive ionisation energies of an element help you work out?

A
  1. The no. of electrons in each shell of atom.

2. Element’s group.

72
Q

What happens to the successive ionisation energies within each shell and why?

A
  1. Successive ionisation energies increase.
  2. Because electrons are being removed from an increasing +ve ion-there’s less repulsion amongst the remaining electrons so they’re held more strongly by the nucleus. Big jumps in ionisation energy happen when a new shell is broken into + electron is being removed from a shell closer to the nucleus.

CHEMISTRY (AS) (24 decks)

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