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

Question 1

Atomic Structure

three types of subatomic particles –

Answer 1

protons, neutrons, and
electrons

Question 2

Atomic Structure

what does an atom contain

Answer 2

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

Question 3

Describe the Plum Pudding Model

Answer 3

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

Question 4

Relative Masses

Define Relative Isotopic Mass

Answer 4

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.

Question 5

Relative Masses

Define Relative Atomic Mass

Answer 5

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.

Question 6

Relative Masses

Define Relative Molecular Mass

Answer 6

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.

Question 7

Relative Masses

Define Relative Formula Mass

Answer 7

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

Question 8

Mass Number & Isotopes

Define Mass number

Answer 8

total number of protons
and neutrons in the nucleus

Question 9

Mass Number & Isotopes

Define Atomic Number

Answer 9

the number of protons.

Question 10

Mass Number & Isotopes

What is mass number

Answer 10

Mass number = number of protons + number of neutrons

Question 11

Mass Number & Isotopes

What is Atomic Number

Answer 11

• Atomic number = number of protons = number of electrons

Question 12

Mass Number & Isotopes

What is an Isotope and its features

Answer 12

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

Question 13

Mass Spectrometry

What is Mass Spectrometry

Answer 13

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

Question 14

Mass Spectrometry

What is the steps of Mass Spectrometry

Answer 14

• Ionisation
• Acceleration
• Ion Drift
• Detection
• Data Analysis

Question 15

Mass Spectrometry

What are the two main techniques of ionisation?

Answer 15

Electrospray ionisation.
Electron impact ionisation

Question 16

Mass Spectrometry

What are the 3 key points about electrospray ionisation?

Answer 16

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

Question 17

Mass Spectrometry

What is electron impact ionisation used for?

Answer 17

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.

Question 18

Mass Spectrometry

How does electrospray ionisation happen? (4 marks)

Answer 18

• 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).

Question 19

Mass Spectrometry

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

Answer 19

X(g) + H+ → X(g) + XH+

Question 20

Mass Spectrometry

How does electron impact ionisation work? (4 marks)

Answer 20

• 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.

Question 21

Mass Spectrometry

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

Answer 21

X(g) + e- → X(g)+

Question 22

Mass Spectrometry

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

Answer 22

• 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

Question 23

Mass Spectrometry

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

Answer 23

(2KE/m)= v^2

Question 24

Mass Spectrometry

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

Answer 24

• 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.

Question 25

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

Answer 25

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

Question 26

Mass Spectrometry Which ions of the three isotopes reach the detector first?

Answer 26

The one with the lowest mass number

Question 27

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

Answer 27

- 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.

Question 28

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

Answer 28

- 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.

Question 29

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

Answer 29

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

Question 30

Mass Spectrometry What does the main peak on the spectrum indicate?

Answer 30

- 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.

Question 31

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

Answer 31

- 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.

Question 32

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

Answer 32

- Because of fragmentation. - The molecule can fragment in the spectrometer - Does not usually happen during electrospray ionisation.

Question 33

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

Answer 33

(80 × 11) + (20 × 10) = 10.8 100

Question 34

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

Answer 34

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

Question 35

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

Answer 35

due to molecular ions that contain different isotopes.

Question 36

Electron Configuration How many main energy levels do atoms contain?

Answer 36

Four

Question 37

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

Answer 37

The s sub-level (1s2)

Question 38

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

Answer 38

s and p sub-levels 1s2, 2s2, 2p6

Question 39

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

Answer 39

s, p and d sub-levels 1s2, 2s2, 2p6, 3s2 3d10

Question 40

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

Answer 40

s p d and f sub-levels

Question 41

Electron Configuration What do sub-levels contain?

Answer 41

Orbitals

Question 42

Electron Configuration How is electronic structure written?

Answer 42

1sⁿ2sⁿ2pⁿ3sⁿ3pⁿ4sⁿ3dⁿ

Question 43

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

Answer 43

* 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

Question 44

Electron Configuration What is the electronic structure of chromium?

Answer 44

1s²2s²2p⁶3s²3p⁶4s¹3d⁵

Question 45

Electron Configuration What is the electronic structure of copper?

Answer 45

1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰

Question 46

Electron Configuration What order are the shells of ions filled?

Answer 46

1sⁿ2sⁿ2pⁿ3sⁿ3pⁿ4sⁿ3dⁿ

Question 47

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

Answer 47

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

Question 48

Ionisation Energy What is ionisation energy?

Answer 48

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

Question 49

Ionisation Energy What units is ionisation energy measured in?

Answer 49

kJmol⁻¹

Question 50

Ionisation Energy What is first ionisation energy?

Answer 50

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

Question 51

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

Answer 51

M(g) → Mⁿ(g) + e⁻

Question 52

Ionisation Energy What are successive ionisation energies?

Answer 52

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

Question 53

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

Answer 53

A decreasing trend

Question 54

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

Answer 54

* 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

Question 55

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?

Answer 55

* 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.

Question 56

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

Answer 56

An increasing trend

Question 57

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

Answer 57

* 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

Question 58

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

Answer 58

* 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

Question 59

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

Answer 59

* 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