Atomic Structure

Question 1

What does a Mass Spectrometer measure?

Answer 1

The relative mass of isotopes

Question 2

What are the stages a Time of Flight mass spectrometer?

Answer 2

• ionisation
• acceleration
• ion drift (distance)
• detection
• analysis

Question 3

Outline Electrospray Ionisation

Answer 3

• sample dissolved in polar solvent
• injected through a needle at a high voltage
• each particle gains a proton (H+) to form 1+ ions

Question 4

What is the equation for electrospray?

Answer 4

X(g) + H+ > XH+(g)

Question 5

What is electron impact?

Answer 5

• high energy electrons fired from electron gun
• knocks of an electron from each particle
• form 1+ ion

Question 6

What is the equation for Electron impact?

Answer 6

X(g) > X+(g) + e-

Question 7

What happenes during Acceleration in TOF?

Answer 7

• positive ions are accelerated by an electric field to a constant KE
( velocity depends in mass of ion)
Ions with lower mass travel faster

Question 8

What happens during Ion Drift in TOF?

Answer 8

• ions separate
• they drift in a flight tube of know distance and time taken is recorded
• TOF depends on velocity

Question 9

What happens during ion detection in TOF?

Answer 9

• positive ions hot detector and pick up an electron
• causes a current to flow
( more ions hitting detector bigger current)

Question 10

Why is a vaccum required in TOF

Answer 10

So no other particles can be detected and interfere

Question 11

Equation for mass(kg) of each 1+ particle

Answer 11

( Mass number/Avagadro ) / 1000

Question 12

Equation to find Velocity with KE and mass

Answer 12

v = √2KE / m

Question 13

What equation can you use if you’re not given distance?

Answer 13

m1 m2
—- = —-
(t1)2 (t2)2

Question 14

What is the formula for relative atomic mass

Answer 14

average mass of an atom of an element
——————————————————-
1/12 mass if an atom an atom of 12C

Question 15

Equation to calculate relative atomic mass from peaks

Answer 15

sum (m/z of a peak x abundance of that peak)
————————————————————
sum of abundances

Question 16

what is fragmentation?

Answer 16

Bonds in covalent bonds break into fragments during electron impact ionisation

Question 17

What happens during fragmentation

Answer 17

fragmentation occur to some not all molecules
they will gain a postitive charge
these give a peak
highest peak = mass number

Question 18

What happen fragmentation happens in Electrospray

Answer 18

little fragmentation occurs so there are less peaks

Question 19

What is the Mr in Electrospray ionisation

Answer 19

the highest peak value minus one

Question 20

What is the Mr in Electron impact?

Answer 20

The peak with the highest m/z value

Question 21

What are shells matching sub-levels??

Answer 21

1 = s
2 = p
3 = d
4 = f

Question 22

What is the order of increasing energy levels?

Answer 22

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s….etc

Question 23

What are the maximum number of electrons in each sublevel

Answer 23

s = 2
p = 6
d = 10
f = 14

Question 24

Why does 4s fill before 3d

Answer 24

4d is lower in energy

Question 25

Why does Cr and Cu differ in electron configuration?

Answer 25

instead of 4s2 they have 4s1
they show a full/half subshell
they have lowere energies and represent more stable arrangements

Question 26

What is first ionisation energy?

Answer 26

The minimum amount of energy required to remove an electron from a gaseous atom

Question 27

What is the trend of Ionisation energy down a group and why?

Answer 27

• decreases
• bc it’s removed from a HIGHER principle energy level
• electron further from
• more sheilding
• less energy required to remove electron

Question 28

What is the trend of Ionisation energy across a group and why?

Answer 28

• increases
• protons increase
• constant sheilding
• more energy needed to remove electrons