3.1.1- Atomic Structure

Question 1

What letter is used to represent the atomic number of an atom?

Answer 1

Z

Question 2

What does the atomic number tell us about an element?

Answer 2

atomic number = number of protons in an atom

Question 3

What letter represents mass number?

Answer 3

A

Question 4

How is the mass number calculated?

Answer 4

number of protons + number of neutrons

Question 5

Define relative atomic mass

Answer 5

mean average mass of all atoms of an element (taking isotopes into account) relative to 1/12 mass of an atom of carbon12

Question 6

What are isotopes of an element?

Answer 6

• different forms of the same element
• have the same number of protons (and electrons) but a different number of neutrons
• they still have the same chemical properties

Question 7

What is the mass of a proton?

Answer 7

1

Question 8

What is the charge of a proton?

Answer 8

+1

Question 9

What is the mass of a neutron?

Answer 9

1

Question 10

What is the charge of a neutron?

Answer 10

0 (no charge)

Question 11

What is the mass of an electron?

Answer 11

0 (negligible)

Question 12

What is the charge of an electron?

Answer 12

-1

Question 13

define ionisation

Answer 13

process in which atoms lose or gain electrons and become ions
- cations (+)
- anions (-)

Question 14

Define 1st ionisation energy

Answer 14

the energy required to remove one electron from one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 15

1st ionisation energy general formula

Answer 15

M(g) = M+(g) + e-(g)

Question 16

2nd ionisation energy general formula

Answer 16

M+(g) = M2+(g) + e-(g)

Question 17

Trends in ionisation energies:
- ionisation energy as more electrons are removed

Answer 17

• more electrons removed = successive ionisation energy increases
  -more significant jumps in ionisation energy where electrons are being removed from the next principle energy level ( as electrons are closer to the nucleus on nearer electron shells so are held more tightly)

Question 18

Trends in ionisation energies:
group 2 elements and 1st ionisation energy

Answer 18

• nuclear charge increases down group 2 but the 1st ionisation energy decreases
• this means electrons are being removed from successively higher energy levels, which lie further from the nucleus and so are less attracted to the nucleus
• outer electrons also ‘shielded’ from nuclear pull by inner shells

Question 19

Trends in ionisation energies
going along a period and ionisation energy (overall trend)

Answer 19

• as you go along a period (L-R), the 1st ionisation energy increases
• this is because as you go along a period, the number of protons in the nucleus increases so the attraction between the nucleus and outer electrons increases
• therefore amount of energy needed to remove an electron increases

Question 20

Why are all ionisation energies endothermic?

Answer 20

• endothermic = positive energy changes and require energy
• endothermic as energy is needed to overcome the electrostatic attraction between electron + nucleus

Question 21

what is an electron shell known as?

Answer 21

principle energy level

Question 22

Max number of electrons for sublevel S

Answer 22

2

Question 23

Max number of electrons for sublevel P

Answer 23

6

Question 24

Max number of electrons for sublevel D

Answer 24

10

Question 25

Max number of electrons for sublevel F

Answer 25

14

Question 26

1st principle energy level: - sub levels -max number of electrons

Answer 26

- sublevels: 1S - max number of electrons: 2

Question 27

2nd principle energy level: - sub levels -max number of electrons

Answer 27

- sublevels: 2S, 2P - max number of electrons: 8

Question 28

3rd principle energy level: - sub levels -max number of electrons

Answer 28

- sublevels: 3S, 3P, 3D - max number of electrons: 18

Question 29

4th principle energy level: - sub levels -max number of electrons

Answer 29

- sublevels: 4S, 4P, 4D, 4F - max number of electrons: 32

Question 30

What does the Aufbau principle state?

Answer 30

lowest energy sublevels are occupied 1st

Question 31

Sub levels (increasing energy)

Answer 31

1S, 2S, 2P, 3S, 3P, 4S, 3D, 4P - positive ions lose electrons from 4S before 3D

Question 32

What is an orbital?

Answer 32

a region around the nucleus than can hold up to two electrons

Question 33

P sublevel -number of orbits -max number of electrons

Answer 33

-number of orbits: 3 - max number of electrons: 6

Question 34

S sublevel -number of orbits -max number of electrons

Answer 34

-number of orbits: 1 - max number of electrons: 2

Question 35

D sublevel -number of orbits -max number of electrons

Answer 35

-number of orbits: 5 - max number of electrons: 10

Question 36

F sublevel -number of orbits -max number of electrons

Answer 36

-number of orbits: 7 - max number of electrons: 14

Question 37

How many electrons can an orbital contain?

Answer 37

no more than 2 electrons (Pauli exclusion principle)

Question 38

What would the relationship between 2 electrons in the same orbital in terms of their spin be?

Answer 38

have opposite spin as they repel each other as they are both negative

Question 39

Hund's rule

Answer 39

single electrons must occupy all empty orbitals within a sublevel before they start to form pairs in orbitals

Question 40

Exceptions: Chromium

Answer 40

- Only has one electron in its 4S orbital before filling 3D 1S(2)...3P(6), 4S(1), 3D(5)

Question 41

Exceptions: Copper

Answer 41

- only has one electron in its 4S orbital before filling 3D -1S(2)...3P(6), 4S(1), 3D(10)

Question 42

Time of flight mass spectrometer - order

Answer 42

- ionisation area - acceleration area - flight path (ion drift) - ion detector

Question 43

Time of flight mass spectrometer - ionisation area method 1

Answer 43

Electrospray: sample is dissolved in a solvent and pushed through a small nozzle at high pressure. a high voltage is applied to it, causing each particle to gain an H+ ion. solvent is then removed, leaving a gas made up of positive ions X (g) + H+ → XH+ (g)

Question 44

Time of flight mass spectrometer - ionisation area method 2

Answer 44

Electron bombardment/impact: normally sample is initially vaporised electron gun (fires high energy electrons) knocks of one electron from each particle to form 1+ molecular ions X (g) → X+ (g) + e-

Question 45

When would you use electron impact/bombardment for ionisation in a mass spectrometer?

Answer 45

for organic or inorganic molecules with a low formula mass

Question 46

When would you use electrospray for ionisation in a mass spectrometer?

Answer 46

for substances with a higher molecular mass including biological molecules e.g. proteins

Question 47

Time of flight mass spectrometer -acceleration

Answer 47

positive ions attracted towards a negatively charged plate. electric field is applied to the ions. each ion receives the same amount of kinetic energy. ions with a lower mass/charge ratio accelerate more quickly so ions with a lower mass experience greater acceleration

Question 48

Time of flight mass spectrometer - ion drift

Answer 48

ions pass through hole in the plate to the flight chamber (where there is no electric field) they drift through it at the same speed as they left the electric field. ions with less mass (lower mas/charge ratio) pass through most quickly

Question 49

Time of flight mass spectrometer -detection

Answer 49

positive ions pick up electrons, current flows (size of current depends on number of ions arriving), m/z value and time of flight recorded. largest current from most abundant ions

Question 50

How to find relative atomic mass

Answer 50

(abundance *relative mass of isotope) /100