Introduction: This unit explores the fundamental principles that form the basis of Chemistry. Wherever possible, candidates should carry out experimental work to illustrate the theoretical principles included in this unit. The development of these skills is associated with the Investigative and Practical Skills detailed in Unit 3.

3.1.1 Atomic Structure

Fundamental particles

Students should

• be able to describe the properties of protons, neutrons and electrons in terms of relative charge and relative mass
• know that early models of atomic structure predicted that atoms and ions with noble gas electron arrangements should be stable

Protons, neutrons and electrons

• understand the importance of these particles in the structure of the atom and appreciate that there are various models to illustrate atomic structure

Mass number and isotopes

• be able to recall the meaning of mass number (A) and atomic (proton) number (Z)
• be able to explain the existence of isotopes
• understand the principles of a simple mass spectrometer, limited to ionisation, acceleration, deflection and detection
• know that the mass spectrometer gives accurate information nabout relative isotopic mass and also about the relative abundance of isotopes
• be able to interpret simple mass spectra of elements and calculate relative atomic mass from isotopic abundance, limited to mononuclear ions
• know that mass spectrometry can be used to identify elements (as used for example in planetary space probes)
• know that mass spectrometry can be used to determine relative molecular mass

Electron arrangement

• know the electron confi gurations of atoms and ions up to Z = 36 in terms of levels and sub-levels (orbitals) s, p and d
• know the meaning of the term ionisation energy.
• understand how ionisation energies in Period 3 (Na . Ar) and in Group 2 (Be . Ba)
• give evidence for electron arrangement in sub-levels and in levels

3.1.2 Amount of Substance

Relative atomic mass and relative molecular mass

• be able to define relative atomic mass (Ar) and relative molecular mass (Mr) in terms of 12C. (The term relative formula mass will be used for ionic compounds)

The mole and the Avogadro constant (L)

• understand the concept of a mole as applied to electrons, atoms, molecules, ions, formulae and equations
• understand the concept of the Avogadro constant. (Calculation not required)

The ideal gas equation

• be able to recall the ideal gas equation pV = nRT and be able to apply it to simple calculations in S.I. units, for ideal gases

Empirical and molecular formulae

• understand the concept of, and the relationship between, empirical and molecular formulae
• be able to calculate empirical formulae from data giving percentage composition by mass

Balanced equations and associated calculations

• be able to write balanced equations (full and ionic) for reactions studied
• be able to balance equations for unfamiliar reactions when reactants and products are specified. (This is an important skill that applies in all units.)
• be able to calculate reacting volumes of gases
• be able to calculate concentrations and volumes for reactions in solutions, limited to titrations of monoprotic acids and bases and examples for which the equations are given
• know that % atom economy = mass of desired product x 100 /total mass of reactants
• be able to calculate reacting masses, % yields and % atom economies from balanced equations

3.1.3 Bonding

Nature of ionic, covalent and metallic bonds

• understand that ionic bonding involves attraction between oppositely charged ions in a lattice
• know that a covalent bond involves a shared pair of electrons
• know that co-ordinate bonding is dative covalency
• understand that metallic bonding involves a lattice of positive ions surrounded by delocalised electrons

Bond polarity

• understand that electronegativity is the power of an atom to withdraw electron density from a covalent bond
• understand that the electron distribution in a covalent bond may not be symmetrical
• know that covalent bonds between different elements will be polar to different extents

Forces acting between molecules

• understand qualitatively how molecules may interact by permanent dipole.dipole, induced dipole-dipole (van der Waals) forces and hydrogen bonding
• understand the importance of hydrogen bonding in determining the boiling points of compounds and the structures of some solids (e.g. ice)

States of matter

• be able to explain the energy changes associated with changes of state
• recognise the four types of crystal: ionic, metallic, giant covalent (macromolecular) and molecular
• know the structures of the following crystals: sodium chloride, magnesium, diamond, graphite, iodine and ice
• be able to relate the physical properties of materials to the type of structure and bonding present

Shapes of simple molecules and ions

• understand the concept of bonding and lone (non bonding) pairs of electrons as charge clouds.
• be able, in terms of electron pair repulsion, to predict the shapes of, and bond angles in, simple molecules and ions, limited to 2, 3, 4, 5 and 6 co-ordination
• know that lone pair/lone pair repulsion is greater than lone pair/bonding pair repulsion, which is greater than bonding pair/bonding pair repulsion, and understand the resulting effect on bond angles

3.1.4 Periodicity

Classification of elements in s, p and d blocks

• be able to classify an element as s, p or d block according to its position in the Periodic Table

Properties of the elements of Period 3

• to illustrate periodic trends
• be able to describe the trends in atomic radius, first ionisation energy, melting and boiling points of the elements Na . Ar
• understand the reasons for the trends in these properties

3.1.5 Introduction to Organic Chemistry

Nomenclature

• know and understand the terms empirical formula, molecular formula, structural formula, displayed formula, homologous series and functional group
• be able to apply IUPAC rules for nomenclature to simple organic compounds, limited to chains with up to 6 carbon atoms limited in this module to alkanes, alkenes and haloalkanes

Isomerism

• know and understand the meaning of the term structural isomerism
• be able to draw the structures of chain, position and functional group isomers

3.1.6 Alkanes

Fractional distillation of crude oil

• know that alkanes are saturated hydrocarbons
• know that petroleum is a mixture consisting mainly of alkane hydrocarbons
• understand that different components (fractions) of this mixture can be drawn off at different levels in a fractionating column because of the temperature gradient

Modification of alkanes by cracking

• understand that cracking involves the breaking of C.C bonds in alkanes
• know that thermal cracking takes place at high pressure and high temperature and produces a high percentage of alkenes (mechanism not required)
• know that catalytic cracking takes place at a slight pressure, high temperature and in the presence of a zeolite catalyst and is used mainly to produce motor fuels and aromatic hydrocarbons (mechanism not required)
• understand the economic reasons for the cracking of alkanes (e.g. ethene used for poly(ethene); conversion of heavy fractions into higher value products)

Combustion of alkanes

• know that alkanes are used as fuels and understand that their combustion can be complete or incomplete and that the internal combustion engine produces a number of pollutants (e.g. NOx, CO and unburned hydrocarbons)
• know that these pollutants can be removed using catalytic converters
• know that combustion of hydrocarbons containing sulfur leads to sulfur dioxide that causes air pollution and
• understand how sulfur dioxide can be removed from flue gases using calcium oxide
• know that the combustion of fossil fuels (including alkanes) results in the release of carbon dioxide into the atmosphere
• know that carbon dioxide, methane and water vapour are referred to as greenhouse gases and that these gases may contribute to global warming