Atomic Structure

Question 1

describe an atom

Answer 1

consists of a nucleus containing protons and neutrons surrounded by electrons

Question 2

what is nuclear force?

Answer 2

its an attractive force being exerted by the nucleus on the electorn in the shells.

Question 3

what happens to the nuclear force across a period

Answer 3

it increases as atomic number increases

Question 4

what happens to nuclear force as we go down the group

Answer 4

it decreases as atomic radius increases

Question 5

when is an atom stable and unstable

Answer 5

stable with full shell and half full, incomplete is unstabke

Question 6

what is electron shielding

Answer 6

is the repulsion between the inner shell electron and the valence shell electron

Question 7

what’s the relationship between shielding effect and atomic number

Answer 7

easier to loose electron the more reactive the metal (greater atomic number)

Question 8

why is it easier to loose electrons as you go down the group?

Answer 8

As we go down the group atomic radius increases
nuclear force decreases because electrons are not as strongly attracted.

the number of electron shells increases as atomic number increases
shedding effect increases as valence electron is not as strongly attracted to the nucleus,
gets easier to loose electron.

Question 9

why is it harder to loose electrons across the period?

Answer 9

Across the period, atomic number increases
atomic radius decreases

but no. of shells remain the same
shielding effect is similar

nuclear force increases, greater force exerted on on valence shell, hence harder to loose electron

Question 10

what are the different sub shells

Answer 10

s,p,d,f

Question 11

describe how many sub shells are the number of electrons each quantum shell holds

Answer 11

1. 1s. 2
2. 2s 2p. 8
3. 3s 3p 3d. 18
4. 4s 4p 4d 4f. 32

Question 12

describe s orbital shape

Answer 12

spherical
size increases with increasing shell number

Question 13

describe p orbital shape

Answer 13

dumbbell shape
x y z axis oriented
lobed become larger and longer with increasing shell number

Question 14

what’s the rule with orbital configuration

Answer 14

fill all the orbits first then you pair them

Question 15

why is zinc and scandium not transition metals

Answer 15

because they only have 1 oxidation state and don’t form coloured compounds

Question 16

what is ionization energy

Answer 16

amount of energy required to remove 1 MOLE of ELECTRONS from 1 MOLE of GASEOUS ATOMS of an element to form 1 MOLE of GASEOUS IONS

Question 17

what is first ionization energy

Answer 17

is the energy required to remove 1 mole of electron from 1 mole of atoms of an element to form 1 mole of +1 ions.

Question 18

Give the first ionization energy of Al

Answer 18

Al –> Al+ + e

Question 19

What is the trend of ionization energy across the period

Answer 19

it increases

Question 20

What is the trend of ionization energy down the group

Answer 20

it decreases

Question 21

4 factors affecting size of ionization energy

Answer 21

1. size of nuclear charge
2. distance of outer electrons from the nucleus
3. sheilding effect of inner electron
4. spin pair repulsion

Question 22

What happens across a period for IE

Answer 22

1. nuclear charge increases
2. same number of shells
3. atomic radius decreases
4. sheilding effect. is similar
5. outer e held tightly, requires more energy to remove

Question 23

How does spin-pair repulsion explain the lower first ionisation energy of oxygen compared to nitrogen?

Answer 23

Oxygen has a pair of electrons in one 2p orbital, so spin-pair repulsion makes it easier to remove an electron than from nitrogen, where all 2p electrons are unpaired.

Question 23

What happens down a group for IE

Answer 23

1. nuclear charge increases
2. more number of shells
3. atomic radius increases
4. sheilding effect increases
5. outer e held less tightly, requiresless energy to remove

Question 24

what are the different stages of TOF

Answer 24

1. ionisation 2. acceleration 3. ion drift 4. ion detection 5. data analysis

Question 25

What are the TOF conditions and why

Answer 25

must be kept in under a high vacuum, to prevent the ions that are produced from colliding with molecules in the air.

Question 26

what are TOF advantages

Answer 26

high sensitivity, high mass accuracy

Question 27

purpose of mass spectrometry

Answer 27

to find 1. relative atomic mass 2. relative molecular mass

Question 28

explain the steps for electron impact ionisation

Answer 28

1. sample is vapourised and injected at low pressure 2. electron gun fires high energy electrons at injected sample. 3. causes outer electron to be knocked off each particle forming +1 ion.

Question 29

why cant we use electron impact ionisation for larger molecules

Answer 29

causes. fragments which accelerate and hit the detector, causes diff peaks on spectrum.

Question 30

explain steps of electrospray ionsation

Answer 30

1. sample dissolved in a volatile and polar solvent. 2. injected at high pressure through a fine hollow needle connected to the +ve terminal of a high voltage supply. 3. molecule gains proton from solvent 4. solvent evaporates into vaccum, ions they move to negative plate.

Question 31

describe what happens during accceleration stage?

Answer 31

positive ions are accelerated to a constant KE by an electric feild towards -ve charged plate.

Question 32

describe what happens during ion drift stage?

Answer 32

ions will pass through a hole in -ve charged plate and move into a flight tube.

Question 33

What happens at the detection stage in TOF mass spectrometry?

Answer 33

Ions hit the detector plate. They gain an electron this gain discharges the ion causing a current to be produced

Question 34

How does the detector measure abundance?

Answer 34

the larger the size of the current, the greater the abundance of ions.

Question 35

Give two reasons why it is necessary to ionise the isotopes of before they can be analysed in a TOF mass spectrometer.

Answer 35

(Ions can be accelerated to a negative plate M2 Ions create a current when hitting the detector

Question 36

How does the mass spectrometer produce 2 diff peaks eg.

Answer 36

1. +ve electron are accelerated by an electric field to a constant kinetic energy The positive ions with m / z of 104 have the same kinetic energy as those with m / z of 118 and move faster Therefore, ions with m / z of 104 arrive at the detector first

Question 37

what happens if a +2 ion is created

Answer 37

it will be affected more by the magnetic feild, prudcing a curved path with smaller radius

Question 38

why is there a big jump?

Answer 38

indicates change in energy level. electron is being removed from an orbital closer to the nucleus so more energy is required

Question 39

why does Al have a lower than expected first IE

Answer 39

has natural spin repulsion in 3p1. reduces amount of neergy required to remove electron

Question 40

why would they use different ionisation methods

Answer 40

electron impact used for organic and inorganic molecules with low formula mass electrospray used for high formula mass eg: proteins