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Chemistry A Level > 3.1.1 Atomic Structure > Flashcards

3.1.1 Atomic Structure Flashcards

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1
Q

What was John Dalton’s model of the atom like? (2)

A

Solid spheres

Different spheres made up different elements

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2
Q

What was JJ Thomson’s model of the atom like? (2)

A

The ‘Plum Pudding’ Model

An atom contains smaller, negatively charged particles (electrons) surrounded by a positively charged ‘pudding’

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3
Q

What was Rutherford’s model of the atom like? (3)

A

A tiny, positively charged nucleus at the centre
A ‘cloud’ of negative electrons surrounding the nucleus
Most of the atom is empty space

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4
Q

What was Bohr’s model of the atom like? (3)

A

Electrons only exist in fixed orbits (shells)
Each shell has a fixed energy
When an electron moves between shells, electromagnetic radiation of fixed frequency is emitted or absorbed

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5
Q

What is the relative charge of a proton?

A

+1

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6
Q

How did the gold foil experiment disprove the plum pudding model?

A

They were expecting most of the alpha particles to be deflected slightly by the ‘pudding’ but most passed straight through the gold foil instead

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7
Q

Why was Rutherford’s model for the atom disproved?

A

If electrons were in a ‘cloud’ around the nucleus, they would quickly spiral down into the nucleus and the atom would collapse

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8
Q

What is the relative mass of a proton?

A

1

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9
Q

What is the relative charge of a neutron?

A

0

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10
Q

What is the relative mass of a neutron?

A

1

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11
Q

What is the relative charge of an electron?

A

-1

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12
Q

What is the relative mass of an electron?

A

1 / 2000

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13
Q

What does the letter A represent?

A

Mass number

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14
Q

What does the letter Z represent?

A

Atomic (proton) number

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15
Q

How is relative atomic mass calculated?

A

(Isotopic mass x percentages) / total percentage

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16
Q

How is relative molecular mass calculated?

A

Add up the relative atomic mass of all atoms in the molecule

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17
Q

What is the difference between relative molecular mass and relative formula mass? (2)

A

Relative formula mass is used on ionic and giant covalent compounds
Relative molecular mass is used used on other molecules

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18
Q

TOF Mass Spectrometry:

Concept (3)

A

Particles of a substance are ionised to form 1+ ions
They are accelerated so they have the same kinetic energy
The time taken to travel a fixed distance is used to find the mass of each ion in the sample

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19
Q

TOF Mass Spectrometry:

Uses (3)

A

Finding the abundance and mass of each isotope in an element allowing us to determine its relative atomic mass
Find the relative molecular mass of substances made of molecules
Identify elements

20
Q

TOF Mass Spectrometry:

Electron Impact / Electron Ionisation (4)

A

The sample is vaporised
An electron gun (a hot wire filament with a current that emits electrons) fires high energy electrons at the vaporised sample
This usually knocks off one electron from each particle, forming a 1+ ion known as a molecular ion
X(g) ➖ X+(g) + e-

21
Q 
TOF Mass Spectrometry:
Electrospray Ionisation (3)
A

The sample is dissolved in a volatile solvent (e.g. water or methanol)
It is injected through a fine hypodermic needle attached to the positive terminal of a high-voltage power supply to give a fine mist (aerosol)
The particles gain a proton (H+) from the solvent as they leave the needle and the solvent evaporates away
X(g) + H+ ➖ XH+(g)

22
Q

TOF Mass Spectrometry:

Which method of ionisation should be used? (2)

A

Electron impact is used for substances with a low formula mass (organic or inorganic)
Electrospray ionisation is used for substances with a higher molecular mass (including biological molecules) such as proteins

23
Q

TOF Mass Spectrometry:

Fragmentation (2)

A

The molecular ion formed from electron impact often breaks down into smaller fragments which are also detected in the mass spectrum
Electrospray ionisation is a ‘soft’ technique so fragmentation rarely takes place

24
Q

TOF Mass Spectrometry:

Acceleration (2)

A

The positive ions are accelerated using an electric field as they are attracted to a negative plate
The field gives the same kinetic energy to all of the ions

25
Q

TOF Mass Spectrometry:

Flight Tube / Ion Drift (3)

A

There is an ion detector at the end of the flight tube
Depending on the velocity of the ion, which in turn depends on the mass of the ion, the time taken to reach the end of the flight tube changes
Lighter particles have a faster velocity and heavier particles have a slower velocity

26
Q

TOF Mass Spectrometry:

Detection (4)

A

The positive ions hit a negatively charged electric plate
The positive ions are discharged by gaining the electrons from the plate
The generated movement of electrons produces a measurable electric current
The size of the current gives a measure of the number of ions hitting the plate

27
Q

TOF Mass Spectrometry:

Mass Spectrum - Electron Impact (3)

A

The signal with the greatest m/z value and abundance is the molecular ion and its m/z value gives the relative molecular mass
The other small peaks that may be present around the molecular ion are due to ions containing different isotopes
There may also be peaks at lower m/z values due to fragmentation

28
Q

TOF Mass Spectrometry:

Mass Spectrum - Electrospray Ionisation (2)

A

The largest peak represents MH+ so the relative molecular mass of the substance is 1 less than the m/z of the peak
Higher peaks may be due to ions containing isotopes

29
Q

What is a sub-shell?

A

Shells are divided into sub-shells which each have a different energy

30
Q

What is an orbital? (2)

A

Sub-shells have different number of orbitals

Orbitals each hold two electrons that pair up due to their opposite spins

31
Q

How many electrons can an S sub-shell hold?

A

2

32
Q

How many electrons can a P sub-shell hold?

A

6

33
Q

How many electrons can a D sub-shell hold?

A

10

34
Q

What is the Aufbau principle?

A

The Aufbau principle states that the lowest energy sub-levels must be filled first

35
Q

What is Hund’s rule? (2)

A

The ‘empty bus seat’ rule

Each sub-level orbital is singly occupied before pairing up begins

36
Q

How do the 4s and 3d sub-shells differ from the general pattern? (2)

A

4s is filled before 3d

During ionisation, 4s empties before 3d

37
Q

How can electron configurations be simplified?

A

Noble gas symbols in square brackets can be used as shorthand to show which sub-levels are already full

38
Q

What is the electron configuration of chromium?

A

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

39
Q

What is the electron configuration of copper?

A

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

40
Q

What is the first ionisation energy?

A

The energy needed to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

41
Q

What is the general formula for the equation for first ionisation energy?

A

X(g) ➖ X+(g) + e-

42
Q

What factors affect ionisation energy? (3)

A

Nuclear charge - the more protons in the nucleus, the more positively charge the nucleus is so the stronger the attraction for the electrons
Distance from nucleus - an electron close to the nucleus will be much more strongly attracted than one further away
Shielding - as the number of electrons between the outer electrons and nucleus increases, the outer electrons feel less attraction to the nucleus

43
Q

What is the general formula for the equation for successive ionisation energies?

A

X(n-1)+ (g) ➖ X(n)+ (g) + e-

44
Q

What is the ionisation trend down group 2? (3)

A

First ionisation decreases down group 2
As each element going down group 2 has one more electron shell, the outer electrons experience the effects of shielding more and they will also be further away from the nucleus
This makes it easier to remove outer electrons, resulting in lower ionisation energies

45
Q

What is the ionisation trend across periods?

A

As you move across periods, generally the ionisation energies increase
This is because the number of protons is increasing so there is a stronger nuclear attraction

46
Q

Why is it easier to remove an electron from shared orbitals?

A

There is repulsion between the two electrons

47
Q

When do big jumps in ionisation occur?

A

Between two different shells as an electron is being removed from a shell closer to the nucleus

Chemistry A Level (32 decks)

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