3.11 - Atomic Structure

Question 1

What are the two types of ionisation and why is it needed

Answer 1

• electrospray
• electron impact

to accelerate and to deflect the beam

Question 2

What is electron spray?

Answer 2

• sample is dissolved in a solvent
• and injected through a needle at high voltage
• each particle gains a proton

X + H+ —> XH+

Question 3

What is electron impact?

Answer 3

• the sample is bombarded by high energy electrons
• the sample electron loses an electron forming M+

Question 4

Define first ionisation energy

Answer 4

The energy required to remove one electron from each atom in a mole of gaseous atoms producing one mole of 1+ gaseous ions

Question 5

What 3 factors affect ionisation energy?

Answer 5

• nuclear charge increases I.E increases bc there’s more protons so stronger attraction for electrons
• distance from nucleus increases I.E decreases
• shielding increases I.E decreases bc less energy required to remove outer electron

Question 6

What is the general ionisation energy trend across periods?

Answer 6

• Ionisation energy increases
• because nuclear charge increases and shielding stays roughly the same
• outer electrons are more attracted to the nucleus

Question 7

Why does the ionisation energy decrease from group 2 to 3?

Answer 7

P orbital is higher energy than S orbital - So easier to lose electron

Question 8

Why does the ionisation energy decrease from group 5 to 6?

Answer 8

Extra electron to electron repulsion make it easier to lose electron

Question 9

KE = ?

Answer 9

1/2mv^2

Question 10

v = ?

Answer 10

Square root: 2KE/m

Question 11

Time of flight (with velocity) =

Answer 11

Length of Flight tube x square root: m/2KE

Question 12

number of moles =

Answer 12

Number of particles / avagadros constant

Question 13

grams to kg = ?

Answer 13

divide by 1000

Question 14

mass of atom (kg)?

Answer 14

mass number/ avagadros constant , then divide that by 1000 to get it in kg

Question 15

What is shielding?

Answer 15

The number of inner electrons - the more inner electrons, the more shielding

Question 16

what’s the electron configuration of Cu?

Answer 16

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10

Question 17

what’s the electron configuration of Cr?

Answer 17

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5

Question 18

What are the different stages of mass spectrometry in order?

Answer 18

1) ionisation (2 types)
2) acceleration
3) flight tube
4) detection

Question 19

Explain how ions are accelerated detected, and have their abundance determined in a spectrometer

Answer 19

• ions accelerated by attraction to negatively charged plate.
• ions detected by gaining electrons
• Abundance, determined by size of current flowing in the detector

Question 20

Define relative atomic mass

Answer 20

Average mass of all isotopes of an element compared to 1/12 the mass of an atom of carbon 12

Question 21

Define relative molecular mass

Answer 21

The weighted average mass of 1 molecule compared to 1/12 the mass of an atom of carbon 12

Question 22

What’s the trend in ionisation energy down a group

Answer 22

• ionisation energy decreases
• atomic radius and shielding increases
• so outer electrons further from the nucleus
• so weaker attraction towards the nucleus

Question 23

What’s the equation for second ionisation energy

Answer 23

X+(g) —> X2+(g) + e-

Question 24

What’s the equation for first ionisation energy

Answer 24

X (g) —> X+(g) + e-

Question 25

what is the evidence for shells?

Answer 25

there is a sharp drop in ionisation energy between the end of 1 period and the start of the next

Question 26

How do you get from cm to m

Answer 26

Divide by 100

Question 27

How do you work out number of neutrons

Answer 27

Mass number - atomic number

Question 28

How is relative abundance measured in a TOF mass spectrometer

Answer 28

Current is proportional to abundance

Question 29

Define 2nd ionisation energy

Answer 29

The enthalpy change when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge

Question 30

What is successive ionisation

Answer 30

The removal of more than 1 electron from the same atom

Question 31

What does it mean if you’re asked to find “ONE MOLE of X” in g

Answer 31

Find the Mr