AS Chemistry OCR A F321 *complete* Notes :)

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David Kemp OCR Chemistry A Unit 1: F321
Atomic Structure
(a) describe protons, neutrons and electrons in
terms of relative charge and relative mass;
Proton Neutron Electron
Relative Charge +1 0 -1
Relative Mass 1 1 1/2000
(b) describe the distribution of mass and charge
Within an atom;
Positively charged Nucleus containing most of the mass, surrounded by atomic shells with orbiting
electrons of negative charge and negligible mass.
(c) describe the contribution of protons and
neutrons to the nucleus of an atom, in terms
of atomic (proton) number and mass
(nucleon) number.
The atomic number of the nucleus, also the proton number, shows the number of protons in the
nucleus. It also defines the element. The number of neutrons added to the number of protons is
the nucleon number or mass number.
Eg. 12C 6 - 12 is the nucleon number, and 6 is the proton number. The number of neutrons can be
found by subtracting the atomic number from the nucleon number.
(d) deduce the numbers of protons, neutrons and
electrons in:
The number of protons is equal to the atomic number, coincidentally so is the number of electrons
in most elements. The number of neutrons can be found by subtracting the proton number from
the mass number.
(i) an atom given its atomic and mass
number,
The element is always given by its proton number.
12
C 6 is Carbon, however 14C 6 is also carbon, albeit an Isotope of carbon.
(e) explain the term isotopes.
Atoms with the same number of protons, although a different number of neutrons.
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David Kemp OCR Chemistry A Unit 1: F321
(f) state that 12C is used as the standard
measurement of relative masses;
(g) define the terms relative isotopic mass and
relative atomic mass, based on the 12C scale;
Relative isotopic mass ­ Mass of an atom of an isotope compared with one twelfth of the mass of
an atom of Carbon 12
Relative atomic mass ­ Average weighted mass of an atom of an element compared with one
twelfth of the mass of an atom of…read more

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David Kemp OCR Chemistry A Unit 1: F321
(d) calculate empirical and molecular formulae,
using composition by mass and percentage
compositions;
Empirical formula = Mass/Percentage of Composition : Mass/Percentage of Composition
Molar Mass Molar Mass
Then divide by the smallest number of moles to find out the ratio.
Chemical Equations
(e) construct balanced chemical equations for
reactions studied and for unfamiliar reactions
given reactants and products;
Things to remember:
1. Group 7, oxygen, nitrogen and hydrogen are diatomic
2.…read more

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David Kemp OCR Chemistry A Unit 1: F321
(g) deduce stoichiometric relationships from
calculations;
Things to remember:
1. Stoichiometric value determines the ratio between the number of moles of a substance.
2. This ratio does not apply to any other calculation apart from working out the number of
moles. After the number of moles is worked out for each substance, the ratio can be
ignored.
(h) use the terms concentrated and dilute as
qualitative descriptions for the concentration
of a solution.…read more

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David Kemp OCR Chemistry A Unit 1: F321
(d) state that an alkali is a soluble base that
releases OH­ ions in aqueous solution;
OH- ions are added to neutralise H+ ions, hence why bases neutralise acids.
(e) state the formulae of the common alkalis:
sodium hydroxide, potassium hydroxide and
aqueous ammonia;
Sodium Hydroxide: NaOH
Potassium Hydroxide: KOH
Ammonia: NH3
Alkali's are special bases that dissolve in water forming aqueous hydroxide ions (OH-)
e.…read more

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David Kemp OCR Chemistry A Unit 1: F321
(h) explain that a base readily accepts H+ ions
from an acid: eg OH­ forming H2O; NH3
forming NH4+
(i) explain the terms anhydrous, hydrated and
water of crystallisation;
Anhydrous: Substance containing no water molecules.
Hydrated: Crystalline compound containing water molecules.
Water of Crystallisation: water molecules that form an essential part of the crystalline structure of
a compound.
(j) calculate the formula of a hydrated salt from
given percentage composition, mass
composition or experimental data;
1.…read more

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David Kemp OCR Chemistry A Unit 1: F321
(ii) changes in oxidation number;
If the oxidation number of an element increases, it is oxidised.
If the oxidation number of an element decreases, it is reduced.
(c) use a Roman numeral to indicate the
magnitude of the oxidation state of an
element, when a name may be ambiguous,
eg nitrate(III) and nitrate(V);
The roman numerals state the oxidation state of an ambiguous element, usually an element from
the transition metals.…read more

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David Kemp OCR Chemistry A Unit 1: F321
Ionisation Energy
(a) Define the terms first ionisation energy and
successive ionisation energy;
First ionisation energy ­ Energy required to remove one electron from each atom in one mole of
gaseous atoms.
Successive ionisation energy ­ energy required to remove each electron in turn.…read more

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David Kemp OCR Chemistry A Unit 1: F321
Electrons: electronic energy levels, shells, sub-shells, atomic orbital's, electron
Configuration
(d) state the number of electrons that can fill the
first four shells;
1st shell ­ 2
2nd shell ­ 8
3rd shell ­ 18
4th shell - 32
(e) describe an orbital as a region that can hold
up to two electrons, with opposite spins;
(f) describe the shapes of s and p orbitals;
s orbitals are spherical and can hold two electrons in total
p…read more

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David Kemp OCR Chemistry A Unit 1: F321
(j) classify the elements into s, p and d blocks.
The s-block of the periodic table consists of the first two groups, plus hydrogen and helium.
The p block of the periodic table is from group 3 to group 0 minus helium
The d block are the transition metals.…read more

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