OCR A LEVEL
CHEMISTRY
NOTES
Covers every spec point!
,2.1 - Atoms and reactions
2.1.1 - Atomic structure and isotopes
The symbols for atomic no. and
mass no. are...
What is the Ar of a proton, 1, 1, and 1/1836 respectively.
neutron, and electron?
Define isotopes Atoms of same element with the same number of protons but different
numbers of neutrons.
What do chemical properties Electronic structure.
depend on?
Thus isotopes have the same chemical properties as they have the same
number of electrons in their outer shell
How do isotopes of the same In physical properties (e.g., density/mp/bp)
element vary?
Define both cation and anion ● Cation - positively charged ion.
● Anion - negatively charged ion.
Define relative isotopic mass The mass of an isotope relative to 1/12 of the mass of an atom of carbon-
12
Define relative atomic mass The weighted mean mass of one atom relative to 1/12 of the mass of one
carbon-12 atom.
What is the formula for the Ar ∑(isotopic mass x relative abundance)
of a sample? Calculation total relative abundance
Careful as total abundance may not always be = 100
How to work out % abundance Pull/ difference x 100
of isotopes? Calculation
What does a mass spectrometer Mass to charge ratio (m/z).
measure?
• Used to determine relative isotopic masses and relative abundances
of isotopes
• Calculation of relative atomic mass of an element from relative
abundances of isotopes
Mass spectrometer steps: ● Sample is placed in mass spectrometer.
, ● Sample is vaporised & ionised to form +ve ions.
● Ions are Accelerated
● Heavier ions move slower.
● They're more difficult to deflect than lighter ions.
● Ions of each isotope are separated.
● Ions are Detected as a mass-to-charge ratio m/z.
● Each ion reaching the detector adds to the signal.
● Greater abundance = Larger signal.
● m/z = Relative mass of ion/relative charge of ion.
● For ions with 1+ charge, ratio = relative isotopic mass.
● This is recorded on the x-axis of the spectrum.
2.1.2 & 2.1.3 - Compounds, formulae, equations, and amount of substance
Formula of a zinc ion Zn2+
Formula of an ammonium ion NH4+
Formula of a silver ion Ag+
Formula of a nitrate ion NO3-
Formula of a nitrite ion NO2-
Formula of a nitride ion N3-
Formula of a carbonate ion CO32-
Formula of a sulfate ion SO42-
Formula of a sulfite ion SO32-
Formula of a phosphate ion PO43-
Formula of a hydrogen HCO3-
carbonate ion
Formula of permanganate ion? MnO4-
Formula of dichromate ion? Cr2O72-
What does a binary compound ONLY two different elements.
contain?
, What is the mnemonic for ● Have No Fear Of Ice Cold Beer.
remembering the diatomic ● H2, N2,, O2, I2, Cl2 Br2.
elements?
What are the steps for writing 1. Balance the equation.
ionic equations? 2. Break each (aq) substance into ions.
3. Cancel any ions on both sides (these being the spectator ions).
What are spectator ions? Ions that aren’t changing state or oxidation number.
Define one mole The amount of substance which contains the same amount of particles as
there are atoms in 12 grams of carbon-12. (ie. 6.02 x 1023 particles)
Define molar mass and molar • Mass per mole given in gmol-1.
gas volume • Gas volume per mole units dm3mol-1
Avogadro’s constant Each mole contains 6.02 x 1023 particles
What is the equation linking mass
mol =
mol (n), mass (m), and molar Mr
mass (Mr)? calculation
What is the equation linking volume of gas(dm^3)
𝑚𝑜𝑙𝑒𝑠 =
mol (n), volume of gas (dm3), 24
and molar gas volume (24 dm3)?
This is used for anything under standard conditions.
calculation
Moles of a solution? calculation Moles = concentration x volume(dm^3)
Define molecular formula The ACTUAL number of atoms of EACH ELEMENT in an element/compound.
Go through calculation steps!
Define empirical formula The SIMPLEST ratio of atoms of EACH ELEMENT in an element/compound.
Go through calculation steps!
CHEMISTRY
NOTES
Covers every spec point!
,2.1 - Atoms and reactions
2.1.1 - Atomic structure and isotopes
The symbols for atomic no. and
mass no. are...
What is the Ar of a proton, 1, 1, and 1/1836 respectively.
neutron, and electron?
Define isotopes Atoms of same element with the same number of protons but different
numbers of neutrons.
What do chemical properties Electronic structure.
depend on?
Thus isotopes have the same chemical properties as they have the same
number of electrons in their outer shell
How do isotopes of the same In physical properties (e.g., density/mp/bp)
element vary?
Define both cation and anion ● Cation - positively charged ion.
● Anion - negatively charged ion.
Define relative isotopic mass The mass of an isotope relative to 1/12 of the mass of an atom of carbon-
12
Define relative atomic mass The weighted mean mass of one atom relative to 1/12 of the mass of one
carbon-12 atom.
What is the formula for the Ar ∑(isotopic mass x relative abundance)
of a sample? Calculation total relative abundance
Careful as total abundance may not always be = 100
How to work out % abundance Pull/ difference x 100
of isotopes? Calculation
What does a mass spectrometer Mass to charge ratio (m/z).
measure?
• Used to determine relative isotopic masses and relative abundances
of isotopes
• Calculation of relative atomic mass of an element from relative
abundances of isotopes
Mass spectrometer steps: ● Sample is placed in mass spectrometer.
, ● Sample is vaporised & ionised to form +ve ions.
● Ions are Accelerated
● Heavier ions move slower.
● They're more difficult to deflect than lighter ions.
● Ions of each isotope are separated.
● Ions are Detected as a mass-to-charge ratio m/z.
● Each ion reaching the detector adds to the signal.
● Greater abundance = Larger signal.
● m/z = Relative mass of ion/relative charge of ion.
● For ions with 1+ charge, ratio = relative isotopic mass.
● This is recorded on the x-axis of the spectrum.
2.1.2 & 2.1.3 - Compounds, formulae, equations, and amount of substance
Formula of a zinc ion Zn2+
Formula of an ammonium ion NH4+
Formula of a silver ion Ag+
Formula of a nitrate ion NO3-
Formula of a nitrite ion NO2-
Formula of a nitride ion N3-
Formula of a carbonate ion CO32-
Formula of a sulfate ion SO42-
Formula of a sulfite ion SO32-
Formula of a phosphate ion PO43-
Formula of a hydrogen HCO3-
carbonate ion
Formula of permanganate ion? MnO4-
Formula of dichromate ion? Cr2O72-
What does a binary compound ONLY two different elements.
contain?
, What is the mnemonic for ● Have No Fear Of Ice Cold Beer.
remembering the diatomic ● H2, N2,, O2, I2, Cl2 Br2.
elements?
What are the steps for writing 1. Balance the equation.
ionic equations? 2. Break each (aq) substance into ions.
3. Cancel any ions on both sides (these being the spectator ions).
What are spectator ions? Ions that aren’t changing state or oxidation number.
Define one mole The amount of substance which contains the same amount of particles as
there are atoms in 12 grams of carbon-12. (ie. 6.02 x 1023 particles)
Define molar mass and molar • Mass per mole given in gmol-1.
gas volume • Gas volume per mole units dm3mol-1
Avogadro’s constant Each mole contains 6.02 x 1023 particles
What is the equation linking mass
mol =
mol (n), mass (m), and molar Mr
mass (Mr)? calculation
What is the equation linking volume of gas(dm^3)
𝑚𝑜𝑙𝑒𝑠 =
mol (n), volume of gas (dm3), 24
and molar gas volume (24 dm3)?
This is used for anything under standard conditions.
calculation
Moles of a solution? calculation Moles = concentration x volume(dm^3)
Define molecular formula The ACTUAL number of atoms of EACH ELEMENT in an element/compound.
Go through calculation steps!
Define empirical formula The SIMPLEST ratio of atoms of EACH ELEMENT in an element/compound.
Go through calculation steps!
