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chemistry > 1.1ATOMIC STRUCTURE, MASS, MASS SPECTROMETRY & ELECTRONIC CONFIGURATION: > Flashcards

1.1ATOMIC STRUCTURE, MASS, MASS SPECTROMETRY & ELECTRONIC CONFIGURATION: Flashcards

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1
Q

Atomic Structure

three types of subatomic particles –

A

protons, neutrons, and
electrons

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2
Q

Atomic Structure

what does an atom contain

A

An atom consists of a nucleus containing protons and neutrons surrounded by electrons.

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3
Q

Describe the Plum Pudding Model

A

After the discovery of electrons, the theory of atoms by which electrons are located in a sea of dispersed positive charge

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4
Q

Relative Masses

Define Relative Isotopic Mass

A

Relative isotopic mass is the mass of an atom of an isotope
compared with 1/12th of the mass of an atom of carbon-12. For
an isotope, the relative isotopic mass = its mass number.

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5
Q

Relative Masses

Define Relative Atomic Mass

A

Relative atomic mass is the ratio of the average mass of
an atom of an element to 1/12th of the mass of an atom of
carbon-12.

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6
Q

Relative Masses

Define Relative Molecular Mass

A

Relative molecular mass is the ratio of the average mass of a
molecule of an element or compound to 1/12th of the mass of
an atom of carbon-12.

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7
Q

Relative Masses

Define Relative Formula Mass

A

Relative formula mass is similar to relative molecular mass but
applies to ionic compounds.

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8
Q

Mass Number & Isotopes

Define Mass number

A

total number of protons
and neutrons in the nucleus

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9
Q

Mass Number & Isotopes

Define Atomic Number

A

the number of protons.

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10
Q

Mass Number & Isotopes

What is mass number

A

Mass number = number of protons + number of neutrons

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11
Q

Mass Number & Isotopes

What is Atomic Number

A
  • Atomic number = number of protons = number of electrons
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12
Q

Mass Number & Isotopes

What is an Isotope and its features

A

same number of protons
different numbers of neutrons.
different mass numbers
same atomic number.
same electronic configuration
different physical properties

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13
Q

Mass Spectrometry

What is Mass Spectrometry

A

molecular chemical analysis
that allows us to:
- find 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

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14
Q

Mass Spectrometry

What is the steps of Mass Spectrometry

A
  • Ionisation
  • Acceleration
  • Ion Drift
  • Detection
  • Data Analysis
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15
Q

Mass Spectrometry

What are the two main techniques of ionisation?

A

Electrospray ionisation.
Electron impact ionisation

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16
Q

Mass Spectrometry

What are the 3 key points about electrospray ionisation?

A
  • a gentler technique and prevents fragmentation.
  • Adds a H⁺, so Mr +1
    -it’s typically used for polymers and biological materials like DNA.
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17
Q

Mass Spectrometry

What is electron impact ionisation used for?

A

is used for elements and substances with low formula mass (that can be inorganic or organic molecules).
When molecules are ionised in this way, the 1+ ion formed is known as a molecular ion.

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18
Q

Mass Spectrometry

How does electrospray ionisation happen? (4 marks)

A
  • the sample X is dissolved in a volatile solvent (eg water or methanol)
  • it is injected through a fine hypodermic needle to give a fine mist (aerosol).
  • the tip of the needle is attached to the positive terminal of a high-voltage power supply.
  • the particles are ionised by gaining a proton (ie an H⁺ ion which is simply one proton) from the solvent as they leave the needle producing XH⁺ ions (ions with a single positive charge and a mass of Mr + 1).
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19
Q

Mass Spectrometry

What’s an equation for electronspray ionisation if the sample is X?

A

X(g) + H+ → X(g) + XH+

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20
Q

Mass Spectrometry

How does electron impact ionisation work? (4 marks)

A
  • the sample is first vaporised and then hit with electrons from an electron gun.
  • The electrons knock off electrons from the molecule
  • The molecules are now positively charged ions.
  • This method often causes the sample to fragment.
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21
Q

Mass Spectrometry

What’s an equation for electron impact ionisation if the sample is X?

A

X(g) + e- → X(g)+

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22
Q

Mass Spectrometry

What happens during Acceleration in the mass spectrometer? (2 marks)

A
  • Molecules are accelerated to all have the same kinetic energy,so the speed is dependent on the mass of the molecule.
  • Lighter particles move faster and are detected before heavier particles
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23
Q

Mass Spectrometry

Given the equation for kinetic energy, the velocity of each particle is given by?

A

(2KE/m)= v^2

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24
Q

Mass Spectrometry

What happens during the ion drift stage of the Mass Spectrometer? (2 marks)

A
  • the positive ions travel through a hole in the negatively charged plate into a tube.
  • the time of flight of each particle through this flight tube depends on its velocity which in turn depends on its mass.
25
Q

Mass Spectrometry

During the ion drift stage what equation can be used to determine the time of flight?

A

Time of flight = Distance / Velocity

t = time of flight (s)
d = length of flight tube (m)
𝑣 = velocity of the particle (m s⁻¹)

26
Q

Mass Spectrometry

Which ions of the three isotopes reach the detector first?

A

The one with the lowest mass number

27
Q

Mass Spectrometry

What is the Detection stage of Mass Spectrometry? (3 marks)

A
  • the ions hit a negatively charged electric plate.
  • when they hit the detector plate, the positive ions are discharged by gaining electrons from the plate. This generates a movement of electrons and hence an electric current that is measured.
  • the size of the current gives a measure of the number of ions hitting the plate.
28
Q

Mass Spectrometry

A computer uses the data to produce a mass spectrum. What does this show? (3 marks)

A
  • the mass to charge (m/z) ratio
  • and abundance of each ion that reaches the detector.
  • given that all ions produced by electrospray ionisation and most of the ions by electron ionisation have a 1+ charge, the m/z is effectively the mass of each ion.
29
Q

Mass Spectrometry

On the spectrum what is the x-axis, and what is the y-axis?

A

The x-axis is mass/charge ratio.
The y-axis is % abundance.

30
Q

Mass Spectrometry

What does the main peak on the spectrum indicate?

A
  • Molecular ion peak.
  • This is the peak of the greatest mass/charge ratio.
  • This represents the mass/charge value of the molecule we are analyzing.
31
Q

Mass Spectrometry

What are the smaller peaks that cluster around the molecular ion peak?

A
  • These are from the same molecules but with different isotopes in them.
  • The isotopic molecules have different masses and so different mass/charge ratio values.
32
Q

Mass Spectrometry

Why do smaller and significantly lighter peaks in the spectrum occur?

A
  • Because of fragmentation.
  • The molecule can fragment in the spectrometer
  • Does not usually happen during electrospray ionisation.
33
Q

Mass Spectrometry

In a mass spectrum of a sample of elemental boron. The spectrum shows that approximately 20% of the boron is ¹⁰B and 80% is ¹¹B.

Calculate the relative atomic mass

A

(80 × 11) + (20 × 10) = 10.8

100

34
Q

Mass Spectrometry

For molecules that are ionised by electron impact how can the molecular ion be identified?

A

the signal with the greatest m/z value is from the molecular ion and its m/z value gives the relative molecular mass.

35
Q

Mass Spectrometry

What other small peaks may be present around the molecular ion, if electron impact ionisation has been used?

A

due to molecular ions that contain different isotopes.

36
Q

Electron Configuration

How many main energy levels do atoms contain?

A

Four

37
Q

Electron Configuration

What sub-level does a first main energy level contain?

A

The s sub-level (1s2)

38
Q

Electron Configuration

What sub-levels does a second main energy level contain?

A

s and p sub-levels

1s2, 2s2, 2p6

39
Q

Electron Configuration

What sub-levels does a third main energy level contain?

A

s, p and d sub-levels

1s2, 2s2, 2p6, 3s2 3d10

40
Q

Electron Configuration

What sub-levels does a fourth main energy level contain?

A

s p d and f sub-levels

41
Q

Electron Configuration

What do sub-levels contain?

A

Orbitals

42
Q

Electron Configuration

How is electronic structure written?

A

1sⁿ2sⁿ2pⁿ3sⁿ3pⁿ4sⁿ3dⁿ

43
Q

Electron Configuration

Why is copper and chromium is an exception to the order in which sub-levels are filled?

A
  • One of the 4s electrons fills the 3d orbital instead
  • This is because a half-filled 3d orbital is more stable than a partially filled 3d orbital
44
Q

Electron Configuration

What is the electronic structure of chromium?

A

1s²2s²2p⁶3s²3p⁶4s¹3d⁵

45
Q

Electron Configuration

What is the electronic structure of copper?

A

1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰

46
Q

Electron Configuration

What order are the shells of ions filled?

A

1sⁿ2sⁿ2pⁿ3sⁿ3pⁿ4sⁿ3dⁿ

47
Q

Electron Configuration

Why are electrons are removed from the 4s sub-level before the 3d sub-level?

A

The electron is always removed from the lowest energy sub-level

48
Q

Ionisation Energy

What is ionisation energy?

A

The energy required to remove one mole of electrons from one mole of gaseous atoms or ions

49
Q

Ionisation Energy

What units is ionisation energy measured in?

A

kJmol⁻¹

50
Q

Ionisation Energy

What is first ionisation energy?

A

The energy required to remove one mole of electrons from one mole of a gaseous neutral atom.

51
Q

Ionisation Energy

What is the general equation for the first ionisation energy of an atom?

A

M(g) → Mⁿ(g) + e⁻

52
Q

Ionisation Energy

What are successive ionisation energies?

A

The ionisation energies required to remove each electron from an atom or ion one after another

53
Q

Ionisation Energy

What is the general trend of the first ionisation energy down group 2?

A

A decreasing trend

54
Q

Ionisation Energy

How does the general trend of first ionisation energy down group 2 show the existence of shells?

A
  • The atomic radius of the elements and size of the atom increases
  • The attraction between the nucleus and outer electron decreases
  • Shells exist as all electrons in an energy level would be the same distance from the nucleus
55
Q

Ionisation Energy

Why do the third successive ionisation energies of group 2 elements show that all elements in a group have the same number of electrons in their highest energy level?

A
  • The third successive ionisation energy of any group 2 element shows a big increase* This is because all electrons have been removed from an s orbital.
56
Q

What is the general trend of first ionisation energies across period 3?

A

An increasing trend

57
Q

Why is the general trend of first ionisation energies across period 3 an increasing trend?

A
  • The number of protons in the nucleus and the nuclear charge of the elements increases
  • The attraction between the outer electron and the nucleus increases
58
Q

How does the deviation of the first ionisation energy of aluminium show that orbitals exist within sub-levels?

A
  • Aluminium has a lower ionisation energy than expected
  • This is because the outer electron is being removed from a 3p orbital
  • The 3p orbital is further away from the nucleus than the 3s orbital
59
Q

Why does the deviation of sulfur show that electrons occupy empty orbitals before pairing up?

A
  • Sulfur has a lower ionisation energy than expected
  • This is because sulfur has a 3p orbital containing two electrons
  • The spin repulsion between them decreases the energy required to remove one of them

chemistry (3 decks)

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