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CHEMISTRY > >>3.1 - Atomic Structure✔ > Flashcards

>>3.1 - Atomic Structure✔ Flashcards

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1
Q

Overall what are the three rules for writing out electron configurations?

A

⓵The lowest energy orbital is filled first.
⓶Electrons with the same spin fill up an orbital first before pairing begins.
⓷No single orbital holds more than 2 electrons.

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2
Q

Give the three isotopes of hydrogen and their composition:

A
  • Protium: 1 proton, 1 electron.
  • Deuterium: 1 proton, 1 neutron, 1 electron.
  • Tritium: 1 proton, 2 neutrons, 1 electron.
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3
Q

What was Daltons model of the atom?

A
  • Proposed all matter was composed of atoms.
  • Indivisible and indestructible ball like structure.
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4
Q

What was the plum pudding model?

A
  • Proposed by JJ Thompson.
  • Atoms consisted of a sphere of positive charge with small negative charges distributed evenly within it.
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5
Q

Describe how we went from Plum Pudding model to Bohr’s model that we use today:

A
  • Due to Rutherford scattering experiment in 1911 it was known that the atom consists of a small dense central nucleus surrounded by orbiting electrons.
  • Bohr proposed electrons orbit in fixed shells or orbitals.
  • James Chadwick provided evidence for the existence of the neutron within the nucleus.
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6
Q

How can we calculate the maximum number of orbiting electrons that can be held by any single shell?

A
  • Using 2n² where ‘n’ is the number of the shell.
  • Each electron shell must fill before the next one can hold any electrons.
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7
Q

What is the mass number represented by and how do we calculate it?

A
  • Represented using A.
  • Sum of protons and neutrons in an atom.
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8
Q

What is the atomic number represented by and what is it it equal to?

A
  • Represented by Z.
  • Equal to the number of protons in an atom.
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9
Q

What is the relative atomic mass (Ar) defined as?

A
  • Average mass of an atom of an element relative to 1/12th the Ar of an atom of carbon-12.
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10
Q

What is an isotope?

A
  • Isotopes are atoms of the same element with the same atomic number (Z) but with a different number of neutrons resulting in a different mass number.
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11
Q

What is the difference in isotopes properties?

A
  • Chemical properties are the same as their proton number and electron configuration are the same.
  • Physical properties are different due to a different mass number.
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12
Q

Give the equation for Ar:
(Of a single atom)

A
  • Relative atomic mass = mass of a single atom/(1/12th x mean mass of carbon-12)
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13
Q

When are ions formed?

A
  • Ions are formed when an atom loses or gains electrons meaning it is no longer neutral and will have an overall charge.
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14
Q

What does time of flight spectrometry record?

A
  • Records the time it takes for ions of each isotope to reach a detector.
  • Using this, spectra can be produced showing each isotope present.
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15
Q

What are the 5 stages to mass spectrometry?

A

⓵Ionisation.
⓶Acceleration.
⓷Ion-drift.
⓸Detection.
⓹Analysis.

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16
Q

Mass Spectrometry:
What is the process in stage ⓵ by electron impact?

A
  • Sample of element is vaporised.
  • High energy electrons are fired at it using an electron gun.
  • Electrons knock an electron off.
  • This leaves +1 charged ions.
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17
Q

Mass Spectrometry:
What is the process in stage ⓵ by electrospray?

A
  • Sample is dissolved in a volatile solvent picking up a H⁺ ion.
  • Its then injected through a hypodermic needle, the tip is attached to a positive terminal of high voltage.
  • This gives a mist.
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18
Q

Mass Spectrometry:
What is the process in stage ⓶?

A
  • Positively charged ions are accelerated towards a negative plate which then switches to positive to repel them forward, this process continues until every ion has equal kinetic energy.
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19
Q

Mass Spectrometry:
What is the process in stage ⓷?

A
  • The ions pass through a hole in the negatively charged plate forming a beam and travel along the flight tube to a detector.
  • Heavier ions travel slower than the lighter ones.
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20
Q

Mass Spectrometry:
What is the process in stage ⓸?

A
  • Positive ions gain electrons when they hit the negatively charged electric plate.
  • This creates an electric current.
  • Size of the current gives a measure of the number of ions hitting the plate (abundance.)
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21
Q

Mass Spectrometry:
In TOF using electron impact; in stage ⓹ what are the three key points?

A
  • Fragmentation is common.
  • Penultimate peak is the Mr (second to last.)
  • The small last peak is there as there could be C-13 present, it is always small.
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22
Q

Mass Spectrometry:
In TOF using electrospray; in stage ⓹ what are the two key points?

A
  • Penultimate peak is the Mr as the next peak has H⁺ attached.
  • Fragmentation is rare.
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23
Q

What is mass spectrometry?

A
  • This is an analytical technique used to identify different isotopes and find the overall relative atomic mass of an element.
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24
Q

During the ionisation process, a 2+ charged ion may be produced, what affect does this have on the spectra?

A
  • Its mass to charge ratio (m/z) is halved.
  • This can be seen on the spectra as a trace at half the expected m/z value.
25
Q

What is the equation for calculating Ar?

A
  • (mass x abundance) + (mass x abundance) / total abundance
26
Q

Describe the spectra produced by the mass spectrometry of an atom of chlorine:

A
  • A characteristic pattern in a 3:1 ratio for Cl⁺ ions.
  • This happens because one isotope is more common than the other.
27
Q

Describe the spectra produced by the mass spectrometry of a chlorine molecule:

A
  • A characteristic pattern in a 9:6:1 ratio for Cl₂⁺ ions.
  • This happens because the chlorine molecule can form in different combinations.
  • We work out the ratio by multiplying the fractions of the abundance of each chlorine atom thats in the molecule.
    e.g: ⁷⁰Cl₂⁺=35+35 → 3/4 x 3/4 = 9/16

⁷²Cl₂⁺=35+37 OR 37+35 → (3/4 x 1/4) + (3/4 x 1/4) = 6/16

⁷⁴Cl₂⁺=37+37 → 1/4 x 1/4 = 1/16

28
Q

Describe the spectra produced by the mass spectrometry of a bromine atom:

A
  • 1:1 ratio for Br⁺ ions.
  • This happens because both isotopes are as common as each other.
29
Q

Describe the spectra produced by the mass spectrometry of a bromine molecule:

A
  • 1:2:1 ratio for Br₂⁺ ions.
  • This happens because the bromine molecule can form in different combinations.
  • We work out the ratio by multiplying the fractions of the abundance of each bromine atom thats in the molecule.

e.g: ¹⁵⁸Br₂⁺=79+79 → 1/2 x 1/2 = 1/4

¹⁶⁰Br₂⁺=79+81 OR 81+79 → (1/2 x 1/2) + (1/2 x 1/2) = 2/4

¹⁶²Br₂⁺=81+81 → 1/2 x 1/2 = 1/4

30
Q

What are electrons held in?

A
  • Held in clouds of negative charge called orbitals.
  • Each orbital can hold up to 2 electrons.
31
Q

What are the different types of orbitals?

A
  • s, p, d and f.
32
Q

What is the shape of an s-orbital?

A
  • Spherical.
33
Q

What is the shape of a p-orbital?

A
  • Dumbbell.
34
Q

What is the shape of a d-orbital?

A
35
Q

Describe the different blocks in the periodic table:

A
  • Each element in the block has its outer electrons in that orbital.
  • S-Block = G1 + G2 and H + He
  • P-Block = G3 - G0
  • D-Block = Transition metals.
  • F-Block = Bottom elements (radioactive.)
36
Q

How many electrons can each orbital hold?
≫S-Orbital:
≫P-Orbital:
≫D-Orbital:
≫F-Orbital:

A
  • 2
  • 6
  • 10
  • 14
37
Q

In what order are orbitals filled and why?

A
  • From s-d.
  • Because the energy of the orbitals increases from s-d.
38
Q

What is the electron configuration of sodium?

A
  • 1s²2s²2p⁶3s¹
39
Q

What is the Pauli exclusion principle?

A
  • No 2 electrons are the same, hence in orbitals they have different spin.
40
Q

Describe what happens within an orbital in terms of spin:

A
  • Electrons pair up with opposite spin so that the atom is as stable as possible.
  • Electrons in the same orbital must have opposite spin.
41
Q

In electron configuration what is the biggest rule we must know about?

A
  • 4s is filled and emptied first before 3d.
  • They are at very similar energy levels.
42
Q

What two elements are exceptions to the rules and what are there electron configurations?

A
  • Cr=1s²2s²2p⁶3s²3p⁶4s¹3d⁵
  • Cu=1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰
  • They take on a different arrangement to improve stability.
43
Q

What is the first ionisation energy defined as?

A
  • The first ionisation energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
44
Q

What is the equation for the first and successive ionisation of a Na atom?
(Up to Na³⁺)

A
  • Na(g) → Na⁺(g) + e⁻
  • Na⁺(g) → Na²⁺(g) + e⁻
  • Na²⁺(g) → Na³⁺(g) + e⁻
45
Q

What occurs with successive ionisations and why?

A
  • Ionisation energy increases.
  • Further electrons are removed which usually requires more energy because as electrons are removed the electrostatic force of attraction between the positive nucleus and the negative outer electrons increases thus more energy is needed.
46
Q

Describe and explain the trend of first ionisation energy along a period:

A
  • First ionisation energy increases.
  • This is due to a decreasing atomic radius with the same shielding and increase in nuclear charge so greater electrostatic forces of attraction.
47
Q

On an ionisation graph what does a sudden large increase indicate and why?

A
  • A change in energy level.
  • This is because the electron is being removed from an orbital closer to the nucleus so more energy is required to do so.
48
Q

What provides supporting evidence for the atomic orbital theory?

A
  • Sudden large increases on ionisation graphs as they indicate a change in energy level.
49
Q

Explain why the first ionisation energy of aluminium is lower than expected:

A
  • Lower than expected due to a single pair of electrons with opposite spin in the same orbital, as a result there is a natural repulsion which reduces the amount of energy needed to be put in to remove the outer electron.
50
Q

Give the two fundamental equations needed for mass spectrometry questions:

A
51
Q

In mass spectrometry questions how do we convert the mass number of an element into kg?

A
  • mass number of element / Avagadros constant

*Then divide by 1000 to convert from grams to kilograms.

52
Q

What does isoelectronic mean?

A
  • Same electron configuration.
53
Q

First ionisation energy across a period

Explain why ionisation energy drops from G2 to G3:

A
  • 2p orbital in G3 elements has higher energy than 2s orbital in G2 element.
  • 2p orbital is further from the nucleus and there is more shielding.
  • Therefore less energy is needed to remove an electron.
54
Q

First ionisation energy across a period

Explain why ionisation energy drops from G5 to G6:

A
  • Electron pair in G6 element repel each other as they are within the same orbital so it is easier to remove.
55
Q

Sketch a graph for the first ionisation energies across period 2:

A
56
Q

Sketch a graph of second ionisation energies across period 2:
(and explain what causes the difference)

A
  • Group 1 now has a full shell so its harder to remove electron.
  • Group 2 has s¹ orbital which is easier to remove.
  • Normal pattern applies.
57
Q

For TOF calculations, if you are only given 2 ion types and the time of flight for one of them and asked to calculate it for the other what formula can we use?

A
  • m/t² = m/t²
58
Q

Describe and explain the trend of first ionisation energy down a group

A
  • First ionisation energy decreases
  • Atoms get bigger
  • more shielding
  • Therefore there is a weaker electrostatic attraction between the nucleus and that electron

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