A-Level Chemistry Edexcel 9CH0

know that ionic bonding is the strong electrostatic attraction between oppositely charged ions

understand that the shape of a simple molecule or ion is determined by the repulsion between the electron pairs that surround a central atom

understand reasons for the shapes of, and bond angles in, simple molecules and ions with up to six outer pairs of electrons (any combination of bonding pairs and lone pairs)

Examples should include BeCl₂, BCl₃, CH₄, NH₃, NH₄⁺, H₂O, CO₂, PCl₅(g) and SF₆(g) and related molecules and ions; as well as simple organic molecules in this specification.

be able to predict the shapes of, and bond angles in, simple molecules and ions analogous to those specified above using electron-pair repulsion theory

know that electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond

know that ionic and covalent bonding are the extremes of a continuum of bonding type and that electronegativity differences lead to bond polarity in bonds and molecules

understand that molecules with polar bonds may not be polar molecules and be able to predict whether or not a given molecule is likely to be polar

understand the nature of intermolecular forces resulting from the following interactions:

i) London forces (instantaneous dipole – induced dipole) ii) permanent dipoles iii) hydrogen bonds

understand the interactions in molecules, such as H₂O, liquid NH₃ and liquid HF, which give rise to hydrogen bonding

understand the following anomalous properties of water resulting from hydrogen bonding:

i) its relatively high melting temperature and boiling temperature ii) the density of ice compared to that of water

be able to predict the presence of hydrogen bonding in molecules analogous to those mentioned above

understand the effects that ionic radius and ionic charge have on the strength of ionic bonding

understand, in terms of intermolecular forces, physical properties shown by materials, including:

i) the trends in boiling temperatures of alkanes with increasing chain length ii) the effect of branching in the carbon chain on the boiling temperatures ofalkanes iii) the relatively low volatility (higher boiling temperatures) of alcohols compared to alkanes with a similar number of electrons iv) the trends in boiling temperatures of the hydrogen halides, HF to HI

understand factors that influence the choice of solvents, including:

i) water, to dissolve some ionic compounds, in terms of the hydration of the ions ii) water, to dissolve simple alcohols, in terms of hydrogen bonding iii) water, as a poor solvent for compounds (to include polar molecules such as halogenoalkanes), in terms of inability to form hydrogen bonds iv) non-aqueous solvents, for compounds that have similar intermolecular forces to those in the solvent

know that metallic bonding is the strong electrostatic attraction between metal ions and the delocalised electrons

know that giant lattices are present in:

i) ionic solids (giant ionic lattices) ii) covalently bonded solids, such as diamond, graphite and silicon (IV) oxide (giant covalent lattices) iii) solid metals (giant metallic lattices)

know that the structure of covalently bonded substances such as iodine, I₂, and ice, H₂O, is simple molecular

know the different structures formed by carbon atoms, including graphite, diamond and graphene

be able to predict the type of structure and bonding present in a substance from numerical data and/or other information

be able to predict the physical properties of a substance, including melting and boiling temperature, electrical conductivity and solubility in water, in terms of:

i) the types of particle present (atoms, molecules, ions, electrons) ii) the structure of the substance iii) the type of bonding and the presence of intermolecular forces, where relevant

understand the formation of ions in terms of electron loss or gain

be able to draw electronic configuration diagrams of cations and anions using dot-and-cross diagrams

understand reasons for the trends in ionic radii down a group and for a set of isoelectronic ions, e.g. N^3– to Al³⁺

understand that the physical properties of ionic compounds and the migration of ions provide evidence for the existence of ions

know that a covalent bond is the strong electrostatic attraction between two nuclei and the shared pair of electrons between them

be able to draw dot-and-cross diagrams to show electrons in covalent substances, including:

i) molecules with single, double and triple bonds ii) species exhibiting dative covalent (coordinate) bonding, including Al₂Cl₆ andammonium ion

understand the relationship between bond lengths and bond strengths for covalent bonds