topic 1- atomic structure

Question 1

underline 2 principles of a TOF mass spectrometer

Answer 1

1. find the mass and abundance of each isotope in an element, allowing the Ar to be determined
2. identify molecules by determining their relative molecular mass

Question 2

underline the 4 different regions of the mass spectrometer

Answer 2

1. ionisation region
2. acceleration region
3. drift region
4. detection

Question 3

what happens in the ionisation region?

Answer 3

the neutral atoms are ionised (lose an electron/ gain a proton) to form +1 ions

Question 4

what are the 2 methods of ionisation

Answer 4

1. electron impact
2. electrospray

Question 5

outline electron impact ionisation

Answer 5

1. sample is vaporised
2. **a beam of high energy electrons is fired from an electron gun **
3. the electron gun has a hot wire filament with a current running through it; heated wire emits electrons
4. electrons are **accelerated by attraction to a positively charged electrode **
5. high energy electrons** knock off only 1 electron **
6. forming a +1 ion
   ** X(g) + e- —–> X+(g) + 2e-**

Question 6

explain what happens in electrospray ionisation

Answer 6

sample is dissolved in a volatile solvent
injected through a hypodermic needle to give a fine mist (aerosol)
the needle tip is attached to the positive terminal of a high voltage power supply
particles are ionised by gaining a proton (H+) from solvent
as they leave the needle producing XH+ ions (ions with a single +ve charge and a Mr of +1)
solvent evaporates and XH+ ions attracted to negative plate

Question 7

explain what happens in the acceleration region

Answer 7

+1 ions accelerated using an electric field to give them all the same kinetic energy

Question 8

what does the speed of each particle depend on (given that kinetic energy is equal)

Answer 8

mass

Question 9

what happens in drift region?

Answer 9

no accelerating field
heavy ions drift more slowly and take longer to reach the detector
lighter ions drift faster and reach the detector first

Question 10

explain what happens in the detection zone

Answer 10

positive ions strike a negatively charged plate
positive ions neutralised as they gain electrons
process generates a flow of electons (electric current)
current is amplified to produce a signal on computer

Question 11

what is m/z

Answer 11

mass to charge ratio

Question 12

the relative intensity of the peak in the resulting mass spectrum produced by __ i__ with a particular __/__ value is proportional to the n_______ of i_____ hitting the p______

Answer 12

the relative intensity of the peak in the resulting mass spectrum produced by** an ion **with a particular m/z value is proportional to the number of ions hitting the plate

Question 13

what is the maximum value of m/z in electron impact

Answer 13

m/z = mr

Question 15

what is the maximum value of m/z in electrospray

Answer 15

m/z = Mr + 1

Question 16

what is the relative atomic mass

Answer 16

the mass of one atom relative to 1/12th the mass of one 12Carbon atom

Question 17

name the subshells can principal energy level 1 can have

Answer 17

s

Question 18

name the subshells can principal energy level 2 can have

Answer 18

s,p

Question 19

name the subshells can principal energy level 3 can have

Answer 19

s,p,d

Question 20

name the subshells can principal energy level 4 can have

Answer 20

s,p,d,f

Question 21

what is the maximum number of orbitals subshell S can have

Answer 21

1

Question 22

what is the maximum number of orbitals subshell p can have

Answer 22

3

Question 23

what is the maximum number of orbitals subshell d can have

Answer 23

5

Question 24

what is the maximum number of orbitals subshell f can have

Answer 24

7

Question 25

maximum number of electrons each orbital can hold

Answer 25

2 (with opposite spin)

Question 26

maximum number of electrons an P orbital can hold

Answer 26

6

Question 27

maximum number of electrons an S orbital can hold

Answer 27

2

Question 28

maximum number of electrons an D orbital can hold

Answer 28

10

Question 29

maximum number of electrons an F orbital can hold

Answer 29

14

Question 30

what is the first ionisation energy of an element?

Answer 30

**the first ionisation energy of an element is defined as the amount of energy required (enthalpy change) to remove 1 mole of electrons from 1 mole of atoms of an element in its gaseous state to form 1 mole of +1 ions **

Question 31

suggest the equation for the first ionisation energy

Answer 31

X(g) ——> X+(g) + e-

Question 32

name the 4 factors that affect ionisation energy

Answer 32

1. atomic radius
2. shielding by inner electrons
3. nuclear charge
4. spin-pair repulsion