2.2.2 Bonding
and structure
Specification
Ionic Bonding
a) ionic bonding as electrostatic attraction between positive and negative ions, and the construction of 'dot-and-cross'
diagrams
(b) explanation of the solid structures of giant ionic lattices, resulting from oppositely charged ions strongly attracted in all
directions e.g. NaCl
(c) explanation of the effect of structure and bonding on the physical properties of ionic compounds, including melting and
boiling points, solubility and electrical conductivity in solid, liquid and aqueous states
Covalent bonding
(d) covalent bond as the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded
atoms
(e) construction of ‘dot-and-cross’ diagrams of molecules and ions to describe: (i) single covalent bonding (ii) multiple
covalent bonding (iii) dative covalent (coordinate) bonding
(f) use of the term average bond enthalpy as a measurement of covalent bond strength
The shapes of simple molecules and ions
(g) the shapes of, and bond angles in, molecules and ions with up to six electron pairs (including lone pairs) surrounding the
central atom as predicted by electron pair repulsion, including the relative repulsive strengths of bonded pairs and lone
pairs of electrons
(h) electron pair repulsion to explain the following shapes of molecules and ions: linear, non-linear, trigonal planar,
pyramidal, tetrahedral and octahedral
Electronegativity and bond polarity
(i) electronegativity as the ability of an atom to attract the bonding electrons in a covalent bond; interpretation of Pauling
electronegativity values
(j) explanation of: (i) a polar bond and permanent dipole within molecules containing covalently-bonded atoms with
different electronegativities (ii) a polar molecule and overall dipole in terms of permanent dipole(s) and molecular shape
Intermolecular forces
(k) intermolecular forces based on permanent dipole–dipole interactions and induced dipole– dipole interactions
(l) hydrogen bonding as intermolecular bonding between molecules containing N, O or F and the H atom of –NH, –OH or HF
(m) explanation of anomalous properties of H2O resulting from hydrogen bonding, e.g.: (i) the density of ice compared with
water (ii) its relatively high melting and boiling points
(n) explanation of the solid structures of simple molecular lattices, as covalently bonded molecules attracted by
intermolecular forces, e.g. I2, ice
(o) explanation of the effect of structure and bonding on the physical properties of covalent compounds with simple
molecular lattice structures including melting and boiling points, solubility and electrical conductivity.
3.1.1 part - Periodic trend in structure and melting point
(d) explanation of: (i) metallic bonding as strong electrostatic attraction between cations (positive ions) and delocalised
electrons (ii) a giant metallic lattice structure, e.g. all metals
(e) explanation of the solid giant covalent lattices of carbon (diamond, graphite and graphene) and silicon as networks of
atoms bonded by strong covalent bonds
(f) explanation of physical properties of giant metallic and giant covalent lattices, including melting and boiling points,
solubility and electrical conductivity in terms of structure and bonding
1
,Covalent bonding
covalent bond as the strong electrostatic attraction between a shared pair of electrons and the nuclei
of the bonded atoms
A molecule is defined as: “two or more atoms which are covalently bonded”
Examples:
Note: In a dot and cross diagram ALL outer electrons should be shown.
Hydrogen Ammonia Carbon dioxide
DO NOT FORGET TO SHOW NON-BONDING ELECTRONS
(f) use of the term average bond enthalpy as a measurement of covalent bond strength (SEE LATER ENERGETICS TOPIC)
2
, Dative Covalent Bonding (Also known as Coordinate Bonding)
A dative covalent bond is a pair of electrons shared between two atoms, but the pair of electrons are donated
by one of the atoms only.
Example: ammonium ion
Ammonium ions, NH4+, are formed by the transfer of a hydrogen ion(H+) from the hydrogen chloride to
the lone pair of electrons on the ammonia molecule.
Question: carbon monoxide
3
and structure
Specification
Ionic Bonding
a) ionic bonding as electrostatic attraction between positive and negative ions, and the construction of 'dot-and-cross'
diagrams
(b) explanation of the solid structures of giant ionic lattices, resulting from oppositely charged ions strongly attracted in all
directions e.g. NaCl
(c) explanation of the effect of structure and bonding on the physical properties of ionic compounds, including melting and
boiling points, solubility and electrical conductivity in solid, liquid and aqueous states
Covalent bonding
(d) covalent bond as the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded
atoms
(e) construction of ‘dot-and-cross’ diagrams of molecules and ions to describe: (i) single covalent bonding (ii) multiple
covalent bonding (iii) dative covalent (coordinate) bonding
(f) use of the term average bond enthalpy as a measurement of covalent bond strength
The shapes of simple molecules and ions
(g) the shapes of, and bond angles in, molecules and ions with up to six electron pairs (including lone pairs) surrounding the
central atom as predicted by electron pair repulsion, including the relative repulsive strengths of bonded pairs and lone
pairs of electrons
(h) electron pair repulsion to explain the following shapes of molecules and ions: linear, non-linear, trigonal planar,
pyramidal, tetrahedral and octahedral
Electronegativity and bond polarity
(i) electronegativity as the ability of an atom to attract the bonding electrons in a covalent bond; interpretation of Pauling
electronegativity values
(j) explanation of: (i) a polar bond and permanent dipole within molecules containing covalently-bonded atoms with
different electronegativities (ii) a polar molecule and overall dipole in terms of permanent dipole(s) and molecular shape
Intermolecular forces
(k) intermolecular forces based on permanent dipole–dipole interactions and induced dipole– dipole interactions
(l) hydrogen bonding as intermolecular bonding between molecules containing N, O or F and the H atom of –NH, –OH or HF
(m) explanation of anomalous properties of H2O resulting from hydrogen bonding, e.g.: (i) the density of ice compared with
water (ii) its relatively high melting and boiling points
(n) explanation of the solid structures of simple molecular lattices, as covalently bonded molecules attracted by
intermolecular forces, e.g. I2, ice
(o) explanation of the effect of structure and bonding on the physical properties of covalent compounds with simple
molecular lattice structures including melting and boiling points, solubility and electrical conductivity.
3.1.1 part - Periodic trend in structure and melting point
(d) explanation of: (i) metallic bonding as strong electrostatic attraction between cations (positive ions) and delocalised
electrons (ii) a giant metallic lattice structure, e.g. all metals
(e) explanation of the solid giant covalent lattices of carbon (diamond, graphite and graphene) and silicon as networks of
atoms bonded by strong covalent bonds
(f) explanation of physical properties of giant metallic and giant covalent lattices, including melting and boiling points,
solubility and electrical conductivity in terms of structure and bonding
1
,Covalent bonding
covalent bond as the strong electrostatic attraction between a shared pair of electrons and the nuclei
of the bonded atoms
A molecule is defined as: “two or more atoms which are covalently bonded”
Examples:
Note: In a dot and cross diagram ALL outer electrons should be shown.
Hydrogen Ammonia Carbon dioxide
DO NOT FORGET TO SHOW NON-BONDING ELECTRONS
(f) use of the term average bond enthalpy as a measurement of covalent bond strength (SEE LATER ENERGETICS TOPIC)
2
, Dative Covalent Bonding (Also known as Coordinate Bonding)
A dative covalent bond is a pair of electrons shared between two atoms, but the pair of electrons are donated
by one of the atoms only.
Example: ammonium ion
Ammonium ions, NH4+, are formed by the transfer of a hydrogen ion(H+) from the hydrogen chloride to
the lone pair of electrons on the ammonia molecule.
Question: carbon monoxide
3
