A* A-Level Physical Chemistry Notes
,Atomic Structure:
Particle Where it’s found Relative mass Relative charge
proton nucleus 1 +1
neutron nucleus 1 0
electron orbitals 1/1840 -1
The atomic number (also known as Z) is defined as the number of protons that are in the nucleus.
The mass number(also known as A) is defined as the total number of protons and neutrons in the
atom.
Isotopes- Atoms of the same element, with the same number of protons, but different number of
neutrons.
Isotopes have similar chemical properties to each other, because they have the same electronic
configuration.
However, they may have different physical properties, because they have different masses.
Time Of Flight Mass Spectrometer:
Mass spectrometers are used to identify elements.
1. Ionisation: There are two different types of ionisation methods that we need to know for A
level Chemistry. They are called electrospray ionisation and electron impact ionisation.
● Electron impact ionisation: The sample analysed is vaporised, under low pressure.
High energy electrons are fired at it. The high energy electrons come from an
“electron gun”. This knocks off one outer electron of each particle, they become +1
ions. E.g. X(g) + e- → X+(g) +2e-
● Electrospray ionisation: The sample is dissolved in a solvent and pushed through a
small nozzle at a high pressure. A high voltage is applied to the small nozzle, causing
the sample molecule to gain a H+ ion. E.g. X(g) + H+ → XH+(g)
2. Acceleration: The positive ions are accelerated by an electric field. The electric field gives the
same KE to all the ions. The lighter ions experience a greater velocity.
, 3. Flight tube: The ions enter a region with no electric field. They drift through it at the same
speed as they left the electric field. So the lighter ions will be drifting at higher speeds.
4. Detection: As lighter ions travel through the drift region at higher speeds, they reach the
detector in less time than heavier ions. When the ions hit the detector, they generate a small
current. The current is generated from the electrons being transferred from the detector to
the positive ions. The amount of current is proportional to the abundance of the isotope.
Worked example:
, Calculating Relative Atomic Mass:
R.A.M= ∑(isotopic mass x % abundance)/100 (If percentage abundance is used)
R.A.M= ∑(isotopic mass x relative abundance)/total relative abundance (if relative abundance is
used)
Electronic configuration:
Electrons are arranged into energy levels (1,2,3,4….), which are then split into sub energy levels called
s,p,d and f.
s holds up to 2 electrons
p holds up to 6 electrons
d holds up to 10 electrons
f holds up to 14 electrons ( do not need to know about f for a levels)
Energy level 1 2 3 4
sub-level 1s 2s,2p 3s,3p,3d 4s,4p,4d,4f
Subshells in atoms are filled up in order of ascending energy. 3d has a higher energy level than 4s, and
is therefore filled before 4s.
Examples:
Electronic configuration for Oxygen: 1s 2s 2p ( this adds up to 8 electrons)
Electronic configuration for Potassium: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ (as you can see 4s filled before 3d, as 3d
has higher energy level)
The periodic table is split into 4 blocks. However, we only need to know about 3 of them, which are
the s block, p block and d block.
S block- elements whose outer electron is in the s orbital are found in the s block. E.g. sodium(1s² 2s²
,Atomic Structure:
Particle Where it’s found Relative mass Relative charge
proton nucleus 1 +1
neutron nucleus 1 0
electron orbitals 1/1840 -1
The atomic number (also known as Z) is defined as the number of protons that are in the nucleus.
The mass number(also known as A) is defined as the total number of protons and neutrons in the
atom.
Isotopes- Atoms of the same element, with the same number of protons, but different number of
neutrons.
Isotopes have similar chemical properties to each other, because they have the same electronic
configuration.
However, they may have different physical properties, because they have different masses.
Time Of Flight Mass Spectrometer:
Mass spectrometers are used to identify elements.
1. Ionisation: There are two different types of ionisation methods that we need to know for A
level Chemistry. They are called electrospray ionisation and electron impact ionisation.
● Electron impact ionisation: The sample analysed is vaporised, under low pressure.
High energy electrons are fired at it. The high energy electrons come from an
“electron gun”. This knocks off one outer electron of each particle, they become +1
ions. E.g. X(g) + e- → X+(g) +2e-
● Electrospray ionisation: The sample is dissolved in a solvent and pushed through a
small nozzle at a high pressure. A high voltage is applied to the small nozzle, causing
the sample molecule to gain a H+ ion. E.g. X(g) + H+ → XH+(g)
2. Acceleration: The positive ions are accelerated by an electric field. The electric field gives the
same KE to all the ions. The lighter ions experience a greater velocity.
, 3. Flight tube: The ions enter a region with no electric field. They drift through it at the same
speed as they left the electric field. So the lighter ions will be drifting at higher speeds.
4. Detection: As lighter ions travel through the drift region at higher speeds, they reach the
detector in less time than heavier ions. When the ions hit the detector, they generate a small
current. The current is generated from the electrons being transferred from the detector to
the positive ions. The amount of current is proportional to the abundance of the isotope.
Worked example:
, Calculating Relative Atomic Mass:
R.A.M= ∑(isotopic mass x % abundance)/100 (If percentage abundance is used)
R.A.M= ∑(isotopic mass x relative abundance)/total relative abundance (if relative abundance is
used)
Electronic configuration:
Electrons are arranged into energy levels (1,2,3,4….), which are then split into sub energy levels called
s,p,d and f.
s holds up to 2 electrons
p holds up to 6 electrons
d holds up to 10 electrons
f holds up to 14 electrons ( do not need to know about f for a levels)
Energy level 1 2 3 4
sub-level 1s 2s,2p 3s,3p,3d 4s,4p,4d,4f
Subshells in atoms are filled up in order of ascending energy. 3d has a higher energy level than 4s, and
is therefore filled before 4s.
Examples:
Electronic configuration for Oxygen: 1s 2s 2p ( this adds up to 8 electrons)
Electronic configuration for Potassium: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ (as you can see 4s filled before 3d, as 3d
has higher energy level)
The periodic table is split into 4 blocks. However, we only need to know about 3 of them, which are
the s block, p block and d block.
S block- elements whose outer electron is in the s orbital are found in the s block. E.g. sodium(1s² 2s²
