Structure of Atoms

define relative atomic mass

the weighted mean mass of an atom of an element compared with 1/12th of the mass od an atom of carbon-12

define isotopic mass

the mass of an atom of an isotope compared with 1/12th of the mass of an atom of carbon-12

name the 2 types of ionisation- mass spectrometry

• electron ionisation

• electrospray ionisation

how is a sample ionised via electron ionisation and give the general equation 

used for elements and low Mr compounds

• sample is vapourised

• high energy electrons fired at it

• knocks off one electron from each particle

• forming 1+ ion  

• X_(g) → X⁺_(g) + e^- 

• ions are then attracted towards a negative electric plate where they are accelerated 

when is electron ionisation used vs electrospray ionisation 

• electron ionisation→ elements with low formula mass, fragmentation can take place

• electrospray ionisation→ higher molecular mass, fragmentation rarely happens

how is a sample ionised via electrospray ionisation and give the general equation 

• sample is dissolved in volatile solvent (e.g. water or methanol)

• injected through a fine hypodermic needle as a fine mist into a vacuum in the ionisation chamber 

• particles are ionised by gaining a proton from the solvent as they leave the needle

• solvent evaporates leaving 1+ ions 

• X_(g) + H⁺ → XH⁺_(g)

as the ionised particles are accelerated, what does this mean for their kinetic energy and therefore velocity

• KE is the same for all particles

• as v= square root 2KE/m

• velocity of each particle depends on its mass

what does the time of flight depend on for each particle 

its velocity, which depends on its mass 

• lighter ions travel faster and reach the detector in less time than heavier particles

when doing ToF calculations, what should KE, distance and mass all be measured in 

KE= J

distance= m

mass= kg

what goes on each axis in a mass spectrum 

x axis- mass/ charge ratio (technically just mass of each ion as each ion has a charge of 1+)

y axis- relative abundance 

why might there be smaller other peaks shown on the mass spectrometer 

due to isotopes of ²H or ¹³C

why might tiny peaks also be formed, but signals may be too small to be seen?

multiple isotopes of the same element 

1. what is the detector

2. what is produced when the ions hit the plate and why

3. what is the size of the current proportional to

1. negatively charged plate

2. current- electrons flow from the plate to the positive ions

3. number of ions

how many electrons can each sub level hold?

1. s

2. p

3. d

4. f

1. 2

2. 6

3. 10

4. 14

when losing electrons, are they lost from 3d or 4s first 

4s, 

give the electron structure of bromine 

mass number = 35

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵

give the electron structure of potassium

mass number= 19

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

give the electron structure of chromium

mass number =24 

ANOMALY

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵

give the electron structure of copper

mass number = 29 

ANOMALY

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰

define 1st ionisation energy

the energy needed to remove one mole of electrons from one mole of gaseous atoms producing one mole of 1+ gaseous ions 

does the first or second ionisation require or energy

second 

which 3 factors effect ionisation energy and how

1. atomic radius- the smaller the radius, the stronger the attraction between the nucleus and the electron

2. number of protons- the more protons, the stronger the attraction between the nucleus and the electron

3. shielding- shielding = repulsion by electrons in shells between the electron and the nucleus) the more shielding, the weaker the attraction between the nucleus and the electron

how does ionisation vary as you go down a group

• ionisation energy decreases

• larger atomic radius

• more shielding

• so weaker attraction between nucleus and electron

how does ionisation vary as you go across a period

• ionisation energy increases

• smaller atomic radius

• more protons

• so stronger attraction between nucleus and the electron

name the two deviations in ionisation energy as u go across a period

general trend- ionisation energy increases

group 2 to 3 dip ( group 3 less than 2)

group 5 to 6 dip ( group 6 less than 5)