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AQA A-Level Chemistry > 3.1.1 Atomic Structure > Flashcards

3.1.1 Atomic Structure Flashcards

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1
Q

Where are protons and neutrons found?

A

Protons and neutrons are found in the centre of the atom called the nucleus.

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2
Q

What can protons and neutrons also be called?

A

Nucleons

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3
Q

Where are electrons found?

A

Electrons surround the nucleus in shells/energy levels.

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4
Q

What are the relative mass and relative charge of a proton?

A

Relative mass= 1
Relative charge= +1

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5
Q

What are the relative mass and relative charge of a neutron?

A

Relative mass= 1
Relative charge= 0

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6
Q

What are the relative mass and relative charge of an electron?

A

Relative mass= 1/1840
Relative charge= -1

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7
Q

Define atomic number.

A

The number of protons in the nucleus.
Same amount of protons and electrons.

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8
Q

Define mass number.

A

Sum of the number of protons and neutrons combined.

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9
Q

What are cations?

A

Positive ions.
An atom that has lost electrons so there is more protons than electrons.
p>e-

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10
Q

What are anions?

A

Negative ions.
An atom that has gained electrons so there is more electrons than protons.
p<e-

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11
Q

Define isotope.

A

Isotopes are atoms of the same element with the same number of protons but a different number of neutrons.

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12
Q

Are the properties of isotopes of the same element the same or different?

A

Isotopes of the same element have the same chemical properties because they have the same electron configuration.

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13
Q

What are the key differences between Thompson’s and Bohr’s models?

A
  • The electrons are kept in the electron shells.
  • There is a small positive nucleus with protons and neutrons.
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14
Q

Define ionisation energy and give an example equation using the first ionisation energy of potassium (K)

A

Ionisation energy is the amount of energy needed to remove a mole of electrons from a mole of atoms in the gaseous state.
e.g. K(g) —> K+(g) + e-

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15
Q

What are the three factors that will influence ionisation energy?

A
  1. Nuclear charge (number of protons in the nucleus)
    Higher nuclear charge= stronger force of attraction between electron and nucleus= higher IE
  2. Distance from nucleus
    If e- is closer to the nucelus= stronger force of attraction= higher IE
  3. Shielding
    Less shielding= stronger force of attraction= higher IE
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16
Q

Why is the second ionisation energy of B higher than the first?

A

The second electron is removed from an ion that already has a positive charge.

17
Q

EXAM QUESTION:
The following data shows the first seven successive IE energies of a period 3 element. State which element it is and explain your reasoning.

1st e- removed = 786.5 kJmol-1
2nd e- removed= 1577.1 kJmol-1
3rd e- removed= 3231.6 kJmol-1
4th e- removed= 4355.5 kJmol-1
5th e- removed= 16091.1 kJmol-1
6th e- removed= 19805.6 kJmol-1
7th e- removed= 23780.4 kJmol-1

A

Silicon
- The largest increase is between the 4th and 5th ionisation energies.
- The 5th electron is on the shell closest to the nucleus.
- The element must have 4 electrons in its outer shell.

18
Q

Why is Li a bigger atom than Be?

A
  • Lithium has fewer protons so it can’t pull its electrons as closely.
  • Both atoms have the same number of shells.
  • They have the same shielding.
  • Be has more protons.
  • So it attracts the outermost electrons more strongly.
19
Q

Why is Li a bigger atom than He?

A
  • Lithium has an extra electron shell and is further away from the nucleus.
  • The outer electron is more shielded.
  • The outer electron is less strongly attracted to the nucleus.
20
Q

Why is Li a bigger atom than F?

A
  • F has more protons, so there is a stronger attraction.
  • Both have the same number of shells.
  • Same shielding,
  • F has more protons so it attracts the outermost electrons more strongly.
21
Q

Why is Li+ a smaller ion than F-?

A
  • Li+ atom only has one shell.
  • Its electrons are closer to the nucleus and there is no shielding.
  • So outer electrons are more strongly attracted.
22
Q

Define an orbital.

A

A region within an atom that can hold up to two electrons with opposite spins.

23
Q

Exceptions for electron configuration.

A
  • Chromium = 1s2 2s2 2p6 3s2 3p6 4s1 3d5
  • Copper= 1s2 2s2 2p6 3s2 3p6 4s1 3d10
  • D block ions= First in, first out. Remove electrons from 4s subshell before 3d subshell.
24
Q

Explain the trend in 1st IE across period 2 elements.

A
  1. General increase in IE across period 2.
  2. Across period 2 there is a greater nuclear charge.
  3. More protons, same shielding
  4. So there is a greater attraction between the nucleus and outer shell.
  5. The first e- from Be is removed from a 2s subshell. The first e- from B is removed from a 2p subshell. 2p subshell is higher in energy than 2s subshell therefore less energy is needed to remove an e- from B.
  6. The first e- removed from N is from a 2p subshell and is unpaired. The first e- removed from O is from a 2p subshell but is from a paired orbital. O has a lower IE due to electron pair repulsion, therefore less energy is needed to remove electrons from O.
25
Q

How does IE change down a group?

A
  1. Atoms get bigger, with more shells.
  2. More shielding.
  3. Weaker attraction from the nucleus to electrons in the outer shell.
  4. IE decreases down the group.
26
Q

State and explain the trend in atomic radius down a group.

A

Down the group atomic radius increases because there are more shells so more shielding. So there is less attraction to the outermost electrons.

27
Q

Why does the atomic radius get smaller from right to left across a period?

A

The nuclear charge (proton number) increases.
Greater attraction between electrons and nucleus.
Same shielding.

28
Q

Stages of a TOF mass spectrometer.

A
  1. Ionisation
  2. Acceleration
  3. Ion drift/Deflection
  4. Detection
29
Q

What are the two methods of ionisation?

A
  1. Electron impact
  2. Electrospray ionisation
30
Q

Explain the method of electron impact ionisation.

A
  1. Sample is vapourised.
  2. High energy electrons from an electron gun are fired at it.
  3. An electron is knocked off each particle, forming a positive ion.

X(g) —> X+(g) + e-

31
Q

Explain the method of electrospray ionisation.

A
  1. Sample is dissolved in a volatile solvent.
  2. Sample is injected through a fine hypodermic needle attached to the positive terminal of a high voltage power supply.
  3. A proton is gained on each particle, forming a positive ion.
32
Q

Why are the sample particles ionised?

A

So they can be accelerated towards the negatively charged plate.
So they generate a current when they gain an electron as they hit the detector.

33
Q

How are ions detected?

A

Each ion hits the detector.
Ion gains an electron.
Generates a current.
Size of current is proportional to the abundance of the ion.

34
Q

Ar and KE formula

A

Ar= (mass 1 x abundance 1) + (mass 2 x abundance 2)/total abundance

KE= 1/2 mv^2
v= d/t

AQA A-Level Chemistry (19 decks)

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