LEVEL TWO CHEMISTRY: STRUCTURE AND BONDING
Electronegativity
Lewis structures
Molecular shapes
Structures of solids
Enthalpy changes
Enthalpy calculations
ELECTRONEGATIVITY:
I can give a definition of electronegativity in terms of an atom’s
ability to attract bonding electrons to itself.
I can describe the general trend of electronegativities in terms
of the periodic table.
I can describe what a covalent bond is by using the terms
‘electrons’ and ‘shared’.
I can show that I understand the implications of electronegativity
by defining the terms ‘polar bond’ and ‘non-polar bond’.
I can draw bond dipoles on given molecules by considering
electronegativities.
LEWIS STRUCTURES:
I can use a periodic table to identify the number of valence
electrons in the atoms of different elements.
I can show that I know that only valence electrons are shown in
Lewis structures by identifying how many electrons need to be
‘shared out’ in the Lewis structure of a given molecule.
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I can show that I understand the octet rule and that electrons
exist in pairs by drawing the Lewis structures of given molecules.
I can show that I understand how many electrons are in single,
double and triple bonds and can draw each type of bond in a
Lewis structure.
MOLECULAR SHAPES:
I can draw the shape of linear, bent, trigonal planar, trigonal
pyramidal and tetrahedral molecules.
I can identify the shapes of molecules from their Lewis structures
by considering the number of areas of electron density around
the central atom and how many bonds the central atom has.
I can explain why examples of molecules have particular
molecular shapes by using terms such as ‘areas of electron
density’ and ‘electron-electron repulsion’.
I can identify a molecule as being polar or non-polar by
considering the polar and non-polar bonds in the molecule as
well as the symmetry of the molecular shape.
STRUCTURES OF SOLIDS:
I can name examples of the following types of solid: ionic,
metallic, molecular and covalent network.
I can compare and contrast the structures and properties of
ionic solids, metallic solids, molecular solids and covalent
network solids by:
Describing what type of particles make up each solid and how these particles are held together in each type of solid (i.e. describing the type of bonding).
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Using my knowledge of the different types of bonding
to explain the extent to which each type of solid exhibits the following properties:
Malleability.
Ductility.
Hardness.
Electrical conductivity.
Melting and boiling points.
Solubility.
I can show that I understand the difference between
intramolecular forces and intermolecular forces by defining
each type of attractive force.
I can discuss how the solubility of polar and non-polar solutes
depends of whether the solvent is polar or non-polar by
describing the attractive forces between the solute and the
solvent in each case.
ENTHALPY CHANGES:
I can show that I understand what exothermic and endothermic
reactions are by describing each in terms of energy.
I can state what the symbol ∆H means and identify whether a
reaction is exothermic or endothermic by considering whether
its ∆H value is negative or positive.
I can explain why bond making is exothermic and bond breaking
is endothermic in terms of the energy required for each process.
I can explain which changes of state are exothermic and which
are endothermic in terms of the energy required for each
process.
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I can draw an enthalpy diagram (including products, reactants,
activation energy and enthalpy change) for an exothermic or
endothermic reaction.
ENTHALPY CALCULATIONS:
I can use calorimetry to calculate the enthalpy change of a
reaction, ΔrH, by using the following equations:
∆T= Tfinal- Tinitial
Q=mc∆T m
M
Q
∆H= n
n= (T = temperature, ΔT = change in temperature)
(Q = energy, m = mass, c = specific heat capacity)
(n = moles, M = molar mass).
(ΔH = change in enthalpy)
Then decide on the sign (+ or –) for ΔH
Finally, write the full thermochemical equation – the
chemical equation with the enthalpy change included at the end.
I can use bond enthalpies to calculate the enthalpy change of a
reaction, ΔrH, by using the following equation:
∆H= ∑(bonds broken) - ∑(bonds made) where bonds
broken are positive and bonds made are negative.
Then write the full thermochemical equation – the chemical equation with the enthalpy change included at the end.
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