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AS Chemistry > Atomic Structure (Redone) > Flashcards

Atomic Structure (Redone) Flashcards

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1
Q

Democritus’s views on particles

A

Made up of atoms which cannot be divided further

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2
Q

Boyle’s views on particles

A

Particles fixed in solids and free in liquids and gases.

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3
Q

Dalton’s views on particles

A

Atoms are indivisible and indestructible. Elements made up of the same atoms and compounds made up of different atoms

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4
Q

JJ Thomson’s views on particles

A

Plum pudding model. Electrons are -vely charged particles which are found in a cloud of positive charge

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5
Q

Rutherford’s views on particles

A

Mass isnt evenly spread, concentrated in the positive nucleus with electrons orbiting it. Electrons kept apart by forces of repulsion. Nucleus made up of protons which he discovered in his scattering experiment.

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6
Q

Explain Rutherford’s scattering experiment

A

Shot alpha particles at a thin foil sheet of gold and expected them to go straight through. Some were deflected

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7
Q

What did Rutherford conclude from his experiment

A

Most of the mass of an atom was concentrated in the centre in the nucleus
Nucleus was +ve to repel the alpha particles
Electrons must orbit the nucleus

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8
Q

Chadwick’s views on particles

A

Discovered neutrons which have same mass as protons but no charge

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9
Q

Bohr’s views on particles

A

Electrons orbit the nucleus in energy levels that have a fixed energy value

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10
Q

Why aren’t protons in the nucleus repelled?

A

Because there’s a strong nuclear force that acts over the nucleus and hold it together into a high density.

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11
Q

Define atomic number

A

The number of protons

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12
Q

Define mass number

A

The total number of protons and neutrons

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13
Q

Define an isotope

A

An atom of an element which has the same number of protons but a different number of neutrons. Same atomic number but different mass number

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14
Q

Why do isotopes have the same chemical properties?

A

Because they have the same electron configuration

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15
Q

Why do isotopes have different physical properties?

A

Because they have a different number of neutrons so they have a different mass

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16
Q

Define relative isotopic mass

A

The mass of a single isotope relative to the mass of 1/12 the mass of an atom of carbon-12.

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17
Q

Define isotopic abundance

A

The percentage of each isotope that occurs naturally on earth

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18
Q

Define relative atomic mass

A

The average mass of an atom of an element relative to 1/12th the mass of an atom of carbon-12.

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19
Q

Why is carbon-12 used as a standard?

A

Because its mass is exactly 12 and it’s practical because it’s a solid

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20
Q

What is mass spectrometry?

A

An instrumental method of analysis

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21
Q

What is mass spec used for?

A

To find Ar and Mr of elements and compounds. Find abundance and mass.

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22
Q

What are the stages of ToF mass spec?

A

Ionisation, Acceleration, Ion drift, Detection

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23
Q

Explain electron impact ionisation

A

Sample is vaporised
High energy electrons fired at it from an electron gun
Electron knocked off to form +ve ion

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24
Q

What is an electron gun

A

Hot wire filament with a current running through it that emits electrons

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25
When is electron impact ionisation used?
For low formula mass compounds
26
Explain electrospray ionisation
Sample dissolved in volatile solvent (water/methanol) Injected through fine hypodermic needle into a mist Tip attached to +ve terminal of high voltage power supply Ionised by gaining proton from solvent Solvent dissolves to just leave sample
27
Write an equation for electron impact
X + e- -----> X+ + 2e-
28
Write an equation for electrospray ionisation
X + H+ -----> XH+
29
For which method does fragmentation occur?
Electron impact
30
Explain acceleration
Positive ions are accelerated using an electric field
31
Why are positive ions accelerated?
So that they all have the same kinetic energy so that some dont move faster bc they have more energy. Velocity based on mass
32
What is the relationship between the mass and the velocity of the particles?
Lighter particles travel faster
33
Why is there a vacuum in the mass spec?
So that the sample ions don't hit the air molecules which will affect their flight path
34
Explain the flight tube
The time taken for positive ions to travel a set distance starting with a constant kinetic energy in an electric field is measured
35
Explain detection
+ve ions hit -ve plate. Discharged by gaining an electron. Movement of electrons causes a current that can be measured.
36
What does the number of peaks in a mass spec tell us?
Number of isotopes
37
What is the molecular ion?
The organic molecule with an electron knocked off to form a positive ion
38
Which peak is the molecular ion peak?
The last major peak at the highest m/z value
39
What is the base peak?
Peak with the greatest abundance
40
How does the distance between energy levels change as you go outwards
Shells get closer
41
What are shells made up of?
Sub shells
42
What are the different sub shells called?
s,p,d,f
43
What are sub shells?
Orbitals or a combination of orbitals
44
What are orbitals?
3D space which can hold up to two electrons
45
Why do electrons in an orbital spin in opposite directions?
To minimise repulsions
46
What's the order of filling sub shells?
!s, 2s, 2p, 3s, 3p, 4s, 3d, 4p
47
Why does the 4s sub shell fill before the 3d?
because the n=3 and n=4 energy levels overlap so the 4s sub shell is lower than 3d
48
What is the ground state of an atom?
When electrons are in their lowest possible energy levels?
49
What ions do metals form and how?
Positive by losing an electron
50
What ions do nonmetals form and how?
Negative by gaining an electron
51
What ions can hydrogen form?
Hydrogen ion H+ or Hydride ion H-
52
What does isoelectronic mean?
Particles with the same electronic configuration
53
What is ionisation?
The process of removing electrons from ions and atoms
54
Define first ionisation energy
The enthalpy change when one mole of electrons is removed from one mole of gaseous atoms, forming one mole of gaseous singly charged cations
55
Define second ionisation energy
The enthalpy change when one mole of electrons is removed from one mole of singly-charged gaseous cations, forming one mole of doubly-charged gaseous cations
56
Write an equation for the first ionisation energy
X(g) ---> X+ + e-
57
Write an equation for the second ionisation energy
X+ ----> X2+ + e-
58
Is ionisation exo or endo?
Endothermic bc energy is required to remove an electron from the attractive forces of the nucleus
59
How can we improve the existence of energy levels?
Successive ionisation energies of an atom show large jumps between shells bc more energy is required bc of increased effective nuclear charge (increase proton:electron ratio)
60
Why does ionisation energy decrease as you go down a group?
Atomic radius increases so outer electrons are further away from the attractive forces of the nucleus More shells = more shielding So less energy required to remove an outer electron
61
Why does first ionisation energy increase across a period?
Nuclear charge increases (more protons) Atomic radius decreases (no extra energy levels) No extra shielding So more energy required to remove the outer electron
62
Why do Group 3 elements show lower than expected ionisation energy?
Division of subshell. 3p1 electron is further from the nucleus and has more shielding so less energy needed to remove it
63
Why do Group 6 elements show lower than expected ionisation energy?
Because they have 4 electrons in the p orbital so there's one pair of electrons so there's repulsion between them so less energy is required
64
Why do Group 1 atoms have the lowest ionisation energies in any period?
Biggest atomic radius (bc lower no of protons) and lowest nuclear charge
65
Why do Group 0 atoms have the highest ionisation energies in any period?
Because they have the smallest atomic radius and the highest nuclear charge
66
How are the patterns in second ionisation energy different to the first?
Shifted one to the left

AS Chemistry (14 decks)

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