Atomic Structure

Question 1

relative masses of sub - atomic particles

Answer 1

proton: 1
neutron: 1
electron: 1/1850

Question 2

relative charges of sub - atomic particles

Answer 2

proton: +1
neutron: 0
electron: -1

Question 3

where are sub - atomic particles found?

Answer 3

protons and neutrons: in the nucleus
electrons: in energy levels

Question 4

what force holds protons and neutrons together?

Answer 4

strong, nuclear force

Question 5

what force holds protons and electrons together?

Answer 5

electrostatic FOA

Question 6

isotope

Answer 6

atoms of the same element with the same number of protons and a different number of neutrons
have the same chemical properties (same electron configuration) and different physical properties (different mass numbers)

Question 7

how to calculate the number of electrons in each energy level

Answer 7

2n^2 (n =2 N³ energy level)
energy levels get higher in energy as you move away from the nucleus (are quantised)

Question 8

What does the quantum model suggest about electron orbitals?

Answer 8

electrons don’t orbit in a well - defined path
It shows complex shapes of orbitals/electron cloud (volume of space where there is likely to be an electron)
Quantum model is based on probability rather than certainty

Question 9

how many orbitals can the s orbital hold?
how many electrons can it hold?
shape?

Answer 9

1 orbital
2 electrons
spherical

Question 10

how many orbitals can the d orbital hold?
how many electrons can it hold?

Answer 10

5 orbitals
10 electrons

Question 11

how many orbitals can the p orbital hold?
how many electrons can it hold?
shape?

Answer 11

3 orbitals
6 electrons
dumbbell shape (drawn as figure of 8)

Question 12

how many orbitals can the f orbital hold?
how many electrons can it hold?

Answer 12

7 orbitals
14 electrons

Question 13

electron spin

Answer 13

electrons have a property called spin
if 2 electrons are in the same orbital, one will spin up and one will spin down

Question 14

When you get to the 3d sub - energy level, what happens?

Answer 14

4s is filled first as it has less energy
4s is further away from the nucleus, so when electrons are lost to form ions, they’re lost from 4s first

Question 15

copper electron configuration

Answer 15

instead of filling 4s first, fill 3d first
1s2 2s2 2p6 3s2 3p6 4s1 3d10

Question 16

chromium electron configuration

Answer 16

fills 1 electron in each 3d orbital to minimise repulsion and give it the lowest energy level possible
1s2 2s2 2p6 3s2 3p6 4s1 3d5

Question 17

ionisation energy

Answer 17

energy required to remove 1 mole of electrons from 1 mole of gaseous atoms or ions to form 1 mole of positive ions
is endothermic as it needs to overcome the attraction between the nucleus and electrons
measured in kJ/mol (when plotting on a graph, use log10 function)

Question 18

1st ionisation energy

Answer 18

enthalpy change needed to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a single positive charge
Mg(g) —- Mg+(g) + e- (need to write state symbols)

Question 19

2nd ionisation energy

Answer 19

enthalpy change needed to remove 1 mole of electrons from 1 mole of gaseous +1 ions to form 1 mole of gaseous ions with a +2 charge
Mg+(g) —- Mg2+(g) + e- (need to write state symbols)

Question 20

enthalpy change

Answer 20

change in heat energy at constant pressure

Question 21

factors affecting ionisation energy

Answer 21

shielding (affects it the most)
nuclear charge
electrons in orbitals

Question 22

how shielding affects ionisation energy

Answer 22

more shielding means lower ionisation energy as there’s a weaker attraction between the outer electron and nucleus which requires less energy to overcome

Question 23

how nuclear charge affects ionisation energy

Answer 23

higher nuclear charge means greater ionisation energy as there’s a stronger attraction between the nucleus and outer electrons so it can pull the electrons more closely (decreased atomic radius)

Question 24

how electrons in orbitals affect ionisation energy

Answer 24

when electrons begin to pair in orbitals, they experience repulsion so it is easier to remove an electron, so it has a lower ionisation energy

Question 25

successive ionisation energy

Answer 25

energy required to remove electrons 1 by 1 from the same atom/ion each time, forming a more highly charged ion F(g) ---- F+(g) + e- F+(g) ---- F2+(g) + 2e- F2+(g) ---- F3+(g) + 3e- F3+(g) ---- F4+(g) + 4e-

Question 26

What is the evidence for different energy levels and the number of electrons in each energy level?

Answer 26

plotting successive ionisation energies show existence of different energy levels and electrons in these energy levels As more electrons are removed, there are large jumps in ionisation energy, which reveal electrons are being removed in the next energy level

Question 27

How to identify the group number the element belongs to, judging from a successive ionisation energy graph

Answer 27

the number of electrons before the first big jump shows the group number of the element If there is no big jump, the element is in group 0 EG: 736 1450 7740 10500 (element is in group 2)

Question 28

trend of ionisation energy across a period

Answer 28

up, down, up, up, down, up, up

Question 29

explain the dip in 1st ionisation energy between beryllium and boron (Be: 1s2 2s2) (B: 1s2 2s2 2p1)

Answer 29

Boron has more energy levels; its outer electron is in the 2p energy level which is further away from the nucleus, so it's easier to remove the electron, so it has a lower ionisation (must write electron configuration)

Question 30

explain the dip in 1st ionisation energy between phosphorus and sulphur (P: 1s2 2s2 2p6 3s2 3p3) (S: 1s2 2s2 2p6 3s2 3p4)

Answer 30

In phosphorus, in the p energy level, electrons are arranged singly in orbitals but in sulphur, they begin to pair and experience repulsion, so electrons are easier to remove, so it has a lower ionisation energy

Question 31

trend of ionisation energies down a group

Answer 31

general decrease due to increase in shielding steep line from Be to Ca then it becomes less steep

Question 32

trend in ionisation from H to Mg

Answer 32

up, down, up, down, up, up, down, up, up, down, up

Question 33

Which ion has the highest ionisation energy? Na: 1s2 2s2 2p6 3s1 Mg+: 1s2 2s2 2p6 3s1

Answer 33

same amount of shielding and number of electrons but magnesium has a higher nuclear charge so it has a higher ionisation energy since there's a stronger attraction between the nucleus and outer electrons

Question 34

trends across period 3: atomic radius 1st ionisation energy electronegativity

Answer 34

atomic radius: decreases 1st ionisation energy: generally increases electronegativity: increases

Question 35

why does the atomic radius of elements decrease across period 3?

Answer 35

higher nuclear charge so the protons are able to attract the electrons more closely (has the same shielding)

Question 36

why does the 1st ionisation energy increase across period 3?

Answer 36

higher nuclear charge with similar shielding so there's a stronger electrostatic attraction between protons and electrons which takes more energy to overcome

Question 37

why does electronegativity increase across period 3?

Answer 37

higher nuclear charge and similar shielding so it can attract electrons more strongly

Question 38

how does melting and boiling point change across period 3?

Answer 38

increases from sodium to silicon (metals increase due to size of ion and having more electrons, and silicon is giant covalent) decreases to phosphorus (P4) then increases to sulfur (S8) as it has more vdW then decreases to chlorine and argon

Question 39

significance of mass spectrometry:

Answer 39

allows us to figure out the Mr of substances helps us see which isotopes make up a certain sample

Question 40

stages of time of flight mass spectrometry:

Answer 40

ionisation acceleration detection

Question 41

conditions of time of flight mass spectrometry:

Answer 41

vacuum (stops electrons from being absorbed by molecules in the air) atoms must be gaseous

Question 42

2 types of ionisation in time of flight mass spectrometry

Answer 42

electron impact (used for elements and low Mr compounds) electrospray (used for high Mr compounds to prevent fragmentation)

Question 43

electron impact ionisation in time of flight mass spectrometry

Answer 43

substance has to be gaseous high energy electrons are fired from an electron gun at the sample to knock off an electron from each atom to form a +1 ion X(g) --- X+ (g) + e-

Question 44

electrospray ionisation in time of flight mass spectrometry

Answer 44

sample dissolved in volatile solvent and injected into a hypodermic needle where particles gain a proton when they leave the needle as a fine mist X + H+ --- XH+ when calculating m/z, you need to take away 1 from each peak as this includes H+ (same for TOF calculations)

Question 45

acceleration in time of flight mass spectrometry

Answer 45

all particles are accelerated so they have the same kinetic energy (only ionised molecules can interact and be accelerated) in the flight tube, ions are accelerated towards a negative plate; their TOF depends on velocities which depend on mass

Question 46

detection in time of flight mass spectrometry

Answer 46

ion picks up electron from a detector to complete the circuit Mg+(g) + e- --- Mg(g) current and abundance are proportional (the higher the current, the greater the abundance of the isotope)

Question 47

m/z ratio in time of flight mass spectrometry

Answer 47

is mass of isotope since charge is +1 (mass/charge) sometimes, 2 electrons can be knocked off in ionisation so the mass is 1/2 than usual

Question 48

RAM equation

Answer 48

(abundance x isotope) + (abundance x isotope)/total abundance

Question 49

how to find the mass of an ion in kg

Answer 49

mr x 10^-3/avogadro's constant

Question 50

molecular ion peak on a mass spectrum

Answer 50

peak with the largest m/z ratio (is the complete molecule that hasn't undergone fragmentation) small peaks on the right of this peak may be due to isotopes such as C13 or H3

Question 51

2 common isotopes of chlorine

Answer 51

Cl35 and Cl37 abundance of 35: 75% abundance 37: 25% relative abundances of Cl35, Cl37 and mix: 9:1:6 (on mass spectrum its m/z ratio is 70, 72 and 74 as it is diatomic and some atoms form in ratio of 3:1)

Question 52

common isotopes of bromine:

Answer 52

Br79 and Br81 abundance of 81 and 79: 50% relative abundance ratio of 79, 81 and mix: 1:1:2 (on mass spectrum its m/z ratio is 158, 160 and 162 as it is diatomic and some atoms form in ratio 1:1)

Question 53

Why do all atoms and compounds have to be ionised in the time of flight spectrometer?

Answer 53

so they can be accelerated by the electric field so ions can create a current when they hit the detector

Question 54

how can you change the acceleration of ions in the spectrometer flight tube?

Answer 54

change the electric field