Atomic Structure

Question 1

what does an atom consist of and what are the charges and mass

Answer 1

nucleus - charge 0 - mass 1
proton - charge 1 - mass 1
electron - charge -1 - mass 0

Question 2

what is the mass number

Answer 2

Mass number = number of protons + number of neutrons

Question 3

what is proton number

Answer 3

Number of protons = mass number - number of neutrons

Question 4

what is an isotope

Answer 4

an atom with same number of protons and electrons but different number of neutrons

Question 5

what is electron impact

Answer 5

• for small molecules
• high energy electrons from electron gun fired at sample
• knocks off one electron (repulsion)
• has to happen in the gas phase

Question 6

what is electrospray

Answer 6

• for large molecules
• sample dissolved in volatile solvent injected as an aerosol through needle
• needle has a high positive charge
• sample gains a H+ ion

Question 7

what is acceleration TOF

Answer 7

• positive ions are accelerated by an negative electric field
• to a constant kinetic energy

Question 8

what is ion drift TOF

Answer 8

the positive ions with smaller m/z values travel faster than those with larger m/z values as they have the same kinetic energy

Question 9

what is detection TOF

Answer 9

• for each isotope the mass spectrometer can measure a m/z ratio and abundance
• each ion of the same mass hits the detector at the same time and each ion gains an electron
• this flow of electrons is a current that is measured and is proportional to abundance

Question 10

what does TOF mean

Answer 10

time of flight

Question 10

what is mass spectrometry used to do

Answer 10

• identify elements
• identify relative molecular mass

Question 10

what is m/z

Answer 10

mass charge ratio

Question 11

what is first ionisation energy

Answer 11

the minimum energy requirement to remove 1 mole of electrons from 1 mole of gaseous atom to form 1 mole of gaseous ions under standard conditions

Question 12

what is trend in first ionisation energy across period

Answer 12

• increased nuclear charge
• atoms get smaller
• stronger attraction from nucleus to valance electrons

Question 13

what causes deviation in group 3

Answer 13

e.e. Al decreases because it has the first electron in 3p which is higher in energy than 3s

Question 14

what causes deviation in group 6

Answer 14

e.g. S has the first spin pair repulsion of electrons in 3p so it is easier to remove

Question 15

what is trend in first ionisation energy down group

Answer 15

• atoms get bigger = larger atomic radius
• more shielding ( when electron in the centre of orbital blocks attraction force from nucleus to outer electrons )
• weaker attraction between nucleus to valance electrons

Question 16

how to recognise which group an element is from based on ionisation energy graph

Answer 16

large increase caused by removing 1st electron from a full shell of electrons (number before increase is the group number)

Question 17

what is special about s block in electron configuration

Answer 17

s fills and empties before d

Question 18

what is the arrangement of cu and cr

Answer 18

Cu - (Ar)4s1 3d10
Cr - (Ar)4s1 3d5
- more energetically favourable for a completely filled or half filled d orbital than a full s orbital