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Chemistry Year 12 Flashcards > Atomic Structure > Flashcards

Atomic Structure Flashcards

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1
Q

What are the three sub-atomic particles of an atom?

A
  • Proton
  • Neutron
  • Electron

Protons are positively charged and located in the nucleus, neutrons are neutral and also in the nucleus, while electrons are negatively charged and found in orbitals.

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2
Q

What does the atomic number represent?

A

The number of protons in the nucleus

The atomic number uniquely identifies an element.

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3
Q

What is the mass number ?

A

The total number of protons and neutrons in the atom

It is calculated as A = Z + Number of Neutrons.

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4
Q

How do you calculate the number of neutrons in an atom?

A

Number of Neutrons = A - Z

A represents the mass number and Z represents the atomic number.

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5
Q

What are isotopes?

A

Atoms with the same number of protons but different numbers of neutrons

Isotopes have similar chemical properties due to the same electronic structure.

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6
Q

What is the purpose of a mass spectrometer?

A

A powerful instrumental method of analysis which is used to:
- find the mass and abundance of each isotope in an element allowing its relative atomic mass to be determined

  • help identify molecules by determining their relative molecular mass

It operates through multiple steps including ionization, acceleration, flight, and detection.

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7
Q

What are the two ionization techniques used in mass spectrometry?

A
  • Electron impact
  • Electrospray ionization

Electron impact is used for smaller molecules, while electrospray is preferred for larger organic molecules.

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8
Q

Fill in the blank: The __________ is the stage in mass spectrometry where positive ions are accelerated by an electric field.

A

Acceleration

This stage ensures ions have constant kinetic energy.

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9
Q

What is the relationship between mass/charge ratio (m/z) and time of flight in mass spectrometry?

A

Lighter ions have shorter flight times compared to heavier ions

This allows for the differentiation of ions based on their m/z values.

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10
Q

What does the relative atomic mass (R.A.M) represent?

A

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

R.A.M can be calculated using the formula: R.A.M = Σ (isotopic mass x % abundance) / 100.

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11
Q

What is a molecular ion in mass spectrometry?

A

The peak that represents the complete molecule in the mass spectrum

It corresponds to the relative molecular mass (Mr) of the molecule.

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12
Q

True or False: In mass spectrometry, fragmentation occurs during electron impact ionization.

A

True

This results in multiple peaks due to the breakdown of the molecule.

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13
Q

What is the first ionization energy?

A

amount of energy required to remove 1 electron from one mole of gaseous atoms forms one mole of gaseous 1+ ions

It is represented by the equation: H(g) → H+(g) + e-.

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14
Q

What is the order of filling sub-levels in electron configuration?

A

1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p

This order is based on increasing energy levels.

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15
Q

How are orbitals filled according to Hund’s rule?

A

Each orbital is filled singly before any orbital is paired

This minimizes electron-electron repulsion within an atom.

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16
Q

What happens to the electronic configuration when a positive ion is formed?

A

Electrons are lost from the outermost shell

For example, Mg loses its 4s electrons when forming Mg2+.

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17
Q

What is the electronic structure of a d-block element?

A

It has complications, as both 4s and 3d sub-shells are involved in filling

Elements like chromium and copper exhibit unusual configurations.

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18
Q

Fill in the blank: The __________ sub-level can hold a maximum of 10 electrons.

A

d

The d sub-level is one of the main sub-level types in electron configurations.

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19
Q

What does the arrangement of electrons in an atom determine?

A

The chemical properties of the element

The electronic structure influences how an atom interacts with others.

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20
Q

What is the equation representing the first ionisation energy?

A

X(g) → X+(g) + e-

The equation always follows the same pattern.

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21
Q

What is the second ionisation energy?

A

The amount of energy required to remove 1 electron from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

Represented by the equation: Ti+(g) → Ti2+(g) + e-.

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22
Q

What are the three main factors that affect ionisation energy?

A
  • The attraction of the nucleus
  • The distance of the electrons from the nucleus
  • Shielding of the attraction of the nucleus

Each factor plays a crucial role in determining the ionisation energy.

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23
Q

Why do successive ionisation energies increase?

A

Each successive ionisation energy is larger due to increased attraction on remaining electrons after one is removed

A positive ion is formed after the first electron removal, increasing the effective nuclear charge.

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24
Q

What does a big jump in successive ionisation energies indicate?

A

It indicates that an electron is being removed from an inner shell closer to the nucleus

This results in a stronger attraction by the nucleus and less shielding.

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25
Why does helium have the largest first ionisation energy?
Its first electron is in the first shell closest to the nucleus with no shielding effects ## Footnote Helium has one more proton than hydrogen, contributing to its higher ionisation energy.
26
Why do first ionisation energies decrease down a group?
Outer electrons are found in shells further from the nucleus and are more shielded ## Footnote This results in a smaller effective nuclear attraction.
27
Why is there a general increase in first ionisation energy across a period?
Electrons are added to the same shell while the number of protons increases, enhancing effective nuclear attraction ## Footnote The distance and shielding effect remain relatively constant.
28
Why does sodium have a much lower first ionisation energy than neon?
Sodium's outer electron is in a 3s shell, further from the nucleus and more shielded ## Footnote This makes Na's outer electron easier to remove.
29
Why is there a small drop in ionisation energy from magnesium to aluminum?
Aluminum begins to fill a 3p subshell, where electrons are slightly easier to remove due to higher energy and shielding ## Footnote The 3p electrons are shielded by 3s electrons.
30
What causes the small drop in ionisation energy from phosphorus to sulfur?
The addition of a second electron to a 3p orbital causes slight repulsion, making it easier to remove ## Footnote This occurs because the second electron experiences repulsion from the first.
31
What is periodicity in the context of ionisation energy?
A repeating pattern across a period that provides useful information about electronic structure ## Footnote The shape of the graph for periods two and three is similar.
32
What pattern is observed in the second ionisation energy graph?
A similar pattern to the first ionisation energy is observed, but shifted one to the left ## Footnote Group 1 elements appear at the peaks of this graph.
33
How is electrospray an advantage over electron impact ionisation? NEED TO DO
Doesn't fragment
34
What is the equation for electrospray ionisation? and method?
M + H --> MH+ Sample is dissolved in a volatile solvent and injected into a thin hypodermic needle to give a fine mist Needle tip is attached to a positive end of a high voltage power supply Particles are ionised and become protonated (gain a proton/hydrogen ion) and form positive ions rest of the sample will evaporate after as it is volatile
35
What is the equation for electron impact ionisation? and method?
M (g) --> M+ (g) + 2e- or the simplified version= M (g) --> M+ (g) + e- Sample is vaporised and high energy electrons are fired at it from an electron gun which has a hot wire filament with a current running through it to allow electrons to be emitted causing it to remove an electron from its outermost shell of gaseous atoms and form positive ions.
36
What can each type of ionisation be used for? electron impact and electrospray? NEED TO DO
Electrospray --> Many substances with high Mr's including biological molecules such as proteins. Electron impact --> used for elements and inorganic and organic molecular substances with low Mr's
37
What are the 4 the steps for a (TOF) Time Of Flight?
Ionisation: electron impact or electrospray. Acceleration Iron drift Detection
38
How does a (TOF) work in short? NEED TO DO
39
Acceleration method
+ ions attract towards (-) charged plate and accelerate towards it. all have same kinetic energy as a result of electric field but ions with lower mass to charge ratio (m/z) are lighter and so experience greater acceleration/move faster heavier ions move slower and receive less acceleration.
40
Iron Drift method NEED TO DO
ions leave the electric field with constant speed and kinetic energy. They enter a region of no electric field and drift through drift tube at same speed they left the electric field ions with a lower m/z ratio will drift faster
41
Detection method NEED TO DO
+ ions strike negatively charged electric plate and are neutralised, gaining an electron. This generates a current at the detector (flow of electrons).
42
Analysis Method
Molecular peaks from on a spectrum graph. Electron impact graph shows a molecular peak of: m/z = Mr And Electrospray: m/z = Mr +1
43
The higher the peak on the mass spectrum graph the higher the....
Abundance, the positive ion has gained an electron and this generates a current (flow of electrons) which is proportionate to the abundance
44
True of False The abundance is directly proportional to the flow of current
True
45
Calculating the Mr of the molecule? NEED TO DO
46
Calculating Molecular ion peak? NEED TO DO
The isotopes come in waves 1st wave is the lightest ion e.g. 24Mg then 25Mg, and then 26Mg
47
What is the difference between the 2 graphs of an electron impact and electrospray mass spectrum graph?
No fragmentation on an electrospray mass spectrum graph.
48
TOF Equations:
V= d/t ---- velocity is equal to distance over time Ke= 1/2 m v*2 ---- Kinetic energy is equal to half the mass times by the velocity squared.
49
Avogadro's Constant
6.022 x 10*23 mol*-1
50
Kg to grams
times by 1000
51
Converting relative mass (Ar) to mass? NEED TO DO
Divide by Avogadro's constant and then divide by 1000 to go back to Kg from grams.
52
Calculating Molecular peaks differences between electron impact and electrospray? NEED TO DO
Need to take an extra proton/hydrogen when calculating molecular peak on an electrospray spectrum graph cos it was gained during electrospray ionisation process.
53
Analysis of the spectrum graphs: Molecular peak? which one? M+1 peak? which one?
Molecular ion peak M+ is the line furthest to the right and this tells us the Mr of the molecule M+1 Peak is the smallest peak to the furthest right and is as a result of C-13 (carbon thirteen) isotope. 1 in 100 carbons are C-13
54
Abundance NEED TO DO
the amount of isotope in the element. A higher current = HIGHER abundance
55
M/Z NEED TO DO
56
History of the atom order
Dalton, J.J Thomson, Rutherford, Bohr, Schrodinger, Chadwick
57
Dalton
Atoms were tiny hard spheres that couldn't be divided or split
58
J.J Thomson
Plum pudding model--> negative electrons embedded in a cloud of positive charge. Mass evenly distributed positively charged no energy levels or nucleus
59
Rutherford
Nuclear model ---> Central positively charged nucleus where most of mass is centred with electrons orbiting on energy levels Gold foil alpha particle scattering experiment... Alpha particles fired at a thing gold foil some went straight through indicating mostly empty space Some rebounded - must have a positive nucleus to repel the alpha particles some deflected- repelled by the positive charge of nucleus.
60
Bohr NEED TO DO
61
Schrodinger NEED TO DO
62
Chadwick NEED TO DO
Discovered neutron exists in the nucleus and is of no charge.
63
Calculating relative atomic mass NEED TO DO
( Mr times by % isotope ) +(Mr times by % isotope ) / 100

Chemistry Year 12 Flashcards (4 decks)

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