P- A.S. =)

Question 1

Give evidence to support that the maximum number of e- that can be accommodated in the s-subshell is 2. (1)

Answer 1

2 elements before drop in IE to Al.

Question 2

Explain why the m/z peak at 31.5 for copper is very small. (1)

Answer 2

• ↑ energy needed to removed 2nd e-

Question 3

Explain how, in a mass spectrometer, ions are detected and how their abundance is measured. (3)

Answer 3

• ions collide w/ detector
• current flows
• abundance ∝ size of current

Question 4

Define the term relative atomic mass. An element exists as a mixture of three isotopes.

Explain, in detail, how the relative atomic mass of this element can be calculated from data obtained from the mass spectrum of the element. (7)

Answer 4

• weighted av. mass of an atom of an element relative to 1/12th the mass of an atom of Carbon-12
• spectrum gives relative abundances
• and m/z
• m/z x relative abundances for each isotope
• add them tgt
• divide by sum of relative abundances

Question 5

Explain the four main stages involved in obtaining the mass spectrum of a sample of gaseous titanium atoms.

Explain why it would be difficult to distinguish between 48Ti2+ and 24Mg+ ions using a mass spectrometer. (10)

Answer 5

1. Ionisation
   – high energy e-
   – knocks e- off
   – +ve ion
2. Acceleration
   – electric field
3. Deflection
   – by magnetic field
4. Detection
   – current flows

• same m/z
• same deflection

Question 6

Outline how the TOF mass spectrometer is able to separate these two species (m/z: 104 & 118) to give two peaks. (4)

Answer 6

• +ve ions accelerated by electric field
• to constant ke
• both ions have same m/z- 104 has higher speed
• 104 arrives at detector first

Question 7

State and explain the trend in the first ionisation energies of the elements in Group 2 from magnesium to barium. (3)

Answer 7

• ↓
• ions get bigger
• ↓ attraction to outer e- ==> more easily lost

Question 8

Explain how ions are accelerated, detected and have their abundance determined in a time of flight mass spectrometer. (3)

Answer 8

• acceleration- attracted to a -ve plate
• detected by gaining e-
• abundance proportional to size of current

Question 9

Explain why the second ionisation energy of calcium is lower than the second ionisation energy of potassium. (2)

Answer 9

• Ca: outer e- further form nucleus
• // e- lost from a higher energy orbital
• ↑ SHIELDING

Question 10

Give one reason why the second ionisation energy of silicon is lower than the second ionisation energy of aluminium. (1)

Answer 10

Si:
- e- removed from 3p
- ↑ in energy
- ↑ shielded

Question 11

Predict the element in period 3 that has the highest second ionisation energy.
Explain why. (2)
/
Period 3: Na Mg Al Si P S Cl Ar

Answer 11

• Na
• e- removed from 2p

Question 12

Explain why the ionisation energy of every element is endothermic. (1)

Answer 12

• Energy needed to overcome
• attraction between -ve e- & +ve nucleus

Question 13

Identify the s-block metal that has the highest first ionisation energy. (1)

Answer 13

Beryllium

x Li ∵ Be has ↑ nuclear charge but x extra shielding

Question 14

Describe how the molecules are ionised using electrospray ionisation. (3)

Answer 14

1. sample dissolved in volatile solvent
2. injected thru +ve ly charged needle at high voltage
3. each molecule gains a proton

Question 15

State how the relative abundance of 185Re+ is determined in a TOF mass spectrometer. (2)

Answer 15

• ion gains an e- at detector
• relative abundance depends on size of current

Question 16

The mass spectrum of the element phosphorus has a peak at m/z = 124.
Give the formula of the species responsible for this peak.
(2)

Answer 16

³¹P₄ +

Question 17

Which atom has the greatest first ionisation energy?
[1 mark]
A H
B He
C Li
D Ne

Answer 17

B

Question 18

Identify the element in Period 3, from sodium to argon, that has the highest second ionisation energy. (1)

Answer 18

Na!!!!!!