TOPIC 3- BONDING AND STRUCTURE.
Ionic bonding
Ionic bonding is the electrostatic attraction between cations
(positive ions) and anions (negative ions).
Ionic compound have giant ionic lattice structures- regular
arrangements of oppositely charged ions.
The strength of an ionic bond is affected by: 1) size of ion
2) charge
of ion
The smaller the ion and larger the charge on the ion, there can be
stronger forces of attraction, therefore stronger ionic bond.
There are two types of evidence for the existence of ions:
1) Electrolysis.
2) Electron density maps
, The ionic radius increases down a group as there are more quantum
shells.
The ionic radius decreases across a period as the number of protons
increases which means the electrons are more strongly attracted to
the nucleus.
Properties of ionic compounds:
1) High melting point- huge lattice structures with strong ionic
bonds and combined forces of attraction requires alot of energy
in order to be broken down. Therefore, ionic compounds have
high melting and boiling points.
2) Brittle (breakable)- when a force is applied to an ionic compound,
layers of ions slide over each other easily and similar ions repel
making the compound brittle.
3) Solid ions do not conduct electricity as they dont contain any
delocalised electrons to carry a charge.
4) Molten/ aqueous compounds can conduct electricity as their ions
become mobile.
5) Most ionic compounds are soluble in water as ‘hydration’
provides energy required to break the lattice structure.
Polarisation: the distortion of the electron cloud of an anion by a
cation.
Polarisation power of a cation is its ability to attract electrons from
the anion towards itself. Cations with a high charge and a small
radius have a higher polarisation power.
Anions with a high charge and a large radius are more easily
polarised as their electron cloud is easily distorted.
When their is polarisation in a compound, the anion undergoes
distortion which makes an area of orbital overlap. This means now
the electrons are rather being shared by the ions.
This causes a degree of covalent bonding in a compound and
decreases the ionic character of a compound.
Covalent bonding.
Covalent bonding is the electrostatic forces of attraction between a
shared pair of electrons and the nuclei of the shared two atoms.
Ionic bonding
Ionic bonding is the electrostatic attraction between cations
(positive ions) and anions (negative ions).
Ionic compound have giant ionic lattice structures- regular
arrangements of oppositely charged ions.
The strength of an ionic bond is affected by: 1) size of ion
2) charge
of ion
The smaller the ion and larger the charge on the ion, there can be
stronger forces of attraction, therefore stronger ionic bond.
There are two types of evidence for the existence of ions:
1) Electrolysis.
2) Electron density maps
, The ionic radius increases down a group as there are more quantum
shells.
The ionic radius decreases across a period as the number of protons
increases which means the electrons are more strongly attracted to
the nucleus.
Properties of ionic compounds:
1) High melting point- huge lattice structures with strong ionic
bonds and combined forces of attraction requires alot of energy
in order to be broken down. Therefore, ionic compounds have
high melting and boiling points.
2) Brittle (breakable)- when a force is applied to an ionic compound,
layers of ions slide over each other easily and similar ions repel
making the compound brittle.
3) Solid ions do not conduct electricity as they dont contain any
delocalised electrons to carry a charge.
4) Molten/ aqueous compounds can conduct electricity as their ions
become mobile.
5) Most ionic compounds are soluble in water as ‘hydration’
provides energy required to break the lattice structure.
Polarisation: the distortion of the electron cloud of an anion by a
cation.
Polarisation power of a cation is its ability to attract electrons from
the anion towards itself. Cations with a high charge and a small
radius have a higher polarisation power.
Anions with a high charge and a large radius are more easily
polarised as their electron cloud is easily distorted.
When their is polarisation in a compound, the anion undergoes
distortion which makes an area of orbital overlap. This means now
the electrons are rather being shared by the ions.
This causes a degree of covalent bonding in a compound and
decreases the ionic character of a compound.
Covalent bonding.
Covalent bonding is the electrostatic forces of attraction between a
shared pair of electrons and the nuclei of the shared two atoms.
