Atomic Structure

Question 1

what is mass spectrometry (MS)

Answer 1

instrumental method to find abundance and mass of each isotope in an element, to determine RAM

Question 2

4 stages in mass spectrometry

Answer 2

ionisation area
acceleration area
ion drift area
detection area

Question 3

what are the two types of ionization

Answer 3

electron impact ionisation
electrospray ionisation

Question 4

what happens during electron impact ionisation?

Answer 4

• sample is vaporized
• high speed electrons fired at it form an electron gun
• electron is knocked off
• positive ions are attracted to a negative electric plate where they are accelerated

Question 5

what can occur during electron impact ionisation?

Answer 5

fragmentation

Question 6

what happens during electrospray ionization?

Answer 6

-sample dissolved in a volatile solvent
- injected through a hypodermic needle to give a mist
- tip of needle attached to a positive terminal of high voltage power supply
-particles gain a proton from solvent producing H+ ions
-solvent evaporate, H+ attracted to the negative plate where they are accelerated

Question 7

what happens during acceleration?

Answer 7

• • ions are attracted towards a negatively charged plate
• accelerates towards it
• lighter ions and more charged ions achieve a higher speed

Question 8

what happens during stage 2 acceleration?

Answer 8

positive ions are accelerated so they all gain kinetic energy

Question 9

what happens during drifting?

Answer 9

ions pass through a hole in the negatively charged plate, forming a beam & travel along the flight tube to a detector

Question 10

what happens during stage 4 detection:

Answer 10

• positive ions gains an electron when they hit the negatively charged plate
• this creates a current
• size of the current shows the abundance of the ions (number of them hitting the plate)

Question 11

what reading do you need to read on the electron impact ionization graph?

Answer 11

penultimate peak
(fragmentation can occur)

Question 12

what reading do you need to read on the electrospray ionization graph? how do we find the Mr from this?

Answer 12

penultimate peak
we must find the subtract 1 to find the Mr as a hydrogen is picked up

Question 13

equation for relative atomic mass

Answer 13

(abundance x mass) + (abundance x mass) / total abundance

Question 14

equation for two isotopes of an element

Answer 14

m(1) / t2(1) = m(2) / t2(2)

Question 15

how to find the mass of an ion

Answer 15

• mass (mass number) / Avogadro constant (6.02 x 10 23)
• divide it by 1000 (to go from grams into kilograms)

Question 16

how do electrons fill energy levels?

Answer 16

starting with the lowest energy level, which is closest to the nucleus

Question 17

how can energy levels be split

Answer 17

sub-shells
orbitals

Question 18

what is an orbital

Answer 18

region of 3d space that has high electron probability density. an orbital can hold a maximum of two electrons

Question 19

1st energy level
maximum number of electrons it can hold?
how many orbitals?

Answer 19

2 electrons
1s orbital

Question 20

2nd energy level
maximum number of electrons it can hold?
how many orbitals?

Answer 20

8 electrons
2s orbital and 3 2p orbitals

Question 21

3rd energy level
maximum number of electrons it can hold?
how many orbitals?

Answer 21

18 electrons
3s, three 3p, five 3d orbitals

Question 22

4th energy level
maximum number of electrons it can hold?
how many orbitals?

Answer 22

32 electrons
4s, three 4p, five 4d, seven 4f orbital

Question 23

what fills up first 4s or 3d

Answer 23

4s always

Question 24

Why are orbitals half filled first?

Answer 24

To reduce repulsion between electrons

Question 25

What is isoelectronic

Answer 25

Same electron configuration

Question 26

What is removed for positive ions

Answer 26

We remove the 4s before the 3d

Question 27

What is the first ionisation energy?

Answer 27

Energy required to form 1 mole of gaseous 1+ ions from 1 mole of gaseous atoms by removing an electron
E.g. Na (g) -> Na+ (g) + e-

Question 28

What is the second ionisation energy

Answer 28

Energy required to form 1 mole of gaseous 2+ ions from 1 mole of gaseous 1+ ion by removing an electron

Question 29

Trend in ionisation energy
Down a group

Answer 29

As you go down the group first ionisation energy decrease ( easier to remove an electron)

Question 30

Why does the ionisation energy decrease down a group

Answer 30

Because
- larger atomic radius
- more shielding from inner shells
(weaker electrostatic attraction between electron & nucleus)
- greater nucleus charge (more protons)

Question 31

What happens with the ionisation energy across a period and why?

Answer 31

Generally it increases. This is because:
- greater nuclear charge
- atomic radius decreases
- similar electron shielding

Question 32

what groups are there a change in pattern in ionization energy across a group

Answer 32

between
2-3
5-6

Question 33

why is there a change in pattern between group 2-3 in ionization energy across a group

Answer 33

the 3p orbital is higher in energy than the 3s orbital. therefore less energy is needed to remove an electron from 3p

Question 34

why is there a change in pattern between group 5-6 in ionization energy across a group

Answer 34

there is an electron pair repelling in the p orbital; therefore less energy required to remove an electron

Question 35

Exceptions in electron configuration
Chromium

Answer 35

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

Question 36

Exception in electron configuration
Copper

Answer 36

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