AQA A LEVEL CHEMISTRY PAPER 1 2025 MARKING
SCHEME
TOF steps - ANS-1) ionisation
2) acceleration
3) ion drift
4) detection
5) analysis
Electron impact - ANS-Sample vaporised and electron gun fires high energy electrons at it which knock
off 1 electron from each particle, making them 1+ ions
NB- can knock off more than one e or break molecular ion
electrospray ionization - ANS-Sample dissolved in volatile solvent then injected through needle to give
fine mist which is attached to positive end of high voltage power supply, particles gain proton
NB- Mr of substance is actually one less than shown due to extra H+
Acceleration (TOF) - ANS-positive ions accelerated using electric field so they all have the same kinetic
energy
Ion drift (TOF) - ANS-particles with small mass have larger velocity do ions start to separate with lightest
ions reaching detector first
Detection (TOF) - ANS-positive ions hit negatively charged plate and gain an electron which forms a
current, the larger the current the higher the abundance
Analysis (TOF) - ANS--computer uses data to produce mass spectrum which shows mass m / charge z
ratio
-mr or ar is furthest right peak (small peaks larger than mr are due to isotopes)
, -may be large peaks at lower mr due to fragmentation
Electron spin - ANS-Property of electron (CW or ACW)
Represented by up and down arrows
Orbitals - ANS-Defined regions of space around nucleus where electrons most likely to be found, each
orbital holds 2 electrons
Hund's Rule - ANS-Electrons prefer to occupy orbitals on their own and only pair up when no empty or
bait ask of same energy are available
Electron configuration - ANS-1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10
exceptions to electron configuration - ANS-chromium and copper, only take one electron in 4s orbital
Why does ionization energy decrease down a group? - ANS-Atoms get bigger so electrons further away
from nucleus, greater shielding
Why does ionization energy increase across a period? - ANS-Atoms get smaller, nuclear charge
increases, similar shielding
Dip in ionisation energy groups 2-3 - ANS-Electrons take up higher orbital (s to p) which makes ionisation
energy lower as higher orbitals have higher energy
Dip in ionisation energy groups 5-6 - ANS-Electron- electron repulsion in orbital makes electron easier to
lose
Relative atomic mass - ANS-The average mass of an atom of an element/ 1/12th of the mass of an atom
of carbon-12
Empirical formula - ANS-The simplest whole number ratio of atoms of each element present in a
compound
SCHEME
TOF steps - ANS-1) ionisation
2) acceleration
3) ion drift
4) detection
5) analysis
Electron impact - ANS-Sample vaporised and electron gun fires high energy electrons at it which knock
off 1 electron from each particle, making them 1+ ions
NB- can knock off more than one e or break molecular ion
electrospray ionization - ANS-Sample dissolved in volatile solvent then injected through needle to give
fine mist which is attached to positive end of high voltage power supply, particles gain proton
NB- Mr of substance is actually one less than shown due to extra H+
Acceleration (TOF) - ANS-positive ions accelerated using electric field so they all have the same kinetic
energy
Ion drift (TOF) - ANS-particles with small mass have larger velocity do ions start to separate with lightest
ions reaching detector first
Detection (TOF) - ANS-positive ions hit negatively charged plate and gain an electron which forms a
current, the larger the current the higher the abundance
Analysis (TOF) - ANS--computer uses data to produce mass spectrum which shows mass m / charge z
ratio
-mr or ar is furthest right peak (small peaks larger than mr are due to isotopes)
, -may be large peaks at lower mr due to fragmentation
Electron spin - ANS-Property of electron (CW or ACW)
Represented by up and down arrows
Orbitals - ANS-Defined regions of space around nucleus where electrons most likely to be found, each
orbital holds 2 electrons
Hund's Rule - ANS-Electrons prefer to occupy orbitals on their own and only pair up when no empty or
bait ask of same energy are available
Electron configuration - ANS-1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10
exceptions to electron configuration - ANS-chromium and copper, only take one electron in 4s orbital
Why does ionization energy decrease down a group? - ANS-Atoms get bigger so electrons further away
from nucleus, greater shielding
Why does ionization energy increase across a period? - ANS-Atoms get smaller, nuclear charge
increases, similar shielding
Dip in ionisation energy groups 2-3 - ANS-Electrons take up higher orbital (s to p) which makes ionisation
energy lower as higher orbitals have higher energy
Dip in ionisation energy groups 5-6 - ANS-Electron- electron repulsion in orbital makes electron easier to
lose
Relative atomic mass - ANS-The average mass of an atom of an element/ 1/12th of the mass of an atom
of carbon-12
Empirical formula - ANS-The simplest whole number ratio of atoms of each element present in a
compound
