Chemistry Notes Topic 2 - Ionic Bonding
Recap:
● When electrons are transferred, ions are formed.
● They can be positive cations or negative anions.
● Simplest ions are single atoms which have achieved a full outer shell.
● Elements will lose or gain electrons to get the full outer shell, and will
therefore form an ion with the same charge (e.g. Mg will lose 2
electrons and become Mg2+).
Ionic Bonding:
● This is the strong electrostatic attraction between oppositely charged
ions.
● The stronger the electrostatic attraction, the stronger the ionic bond.
● When oppositely charged ions form an ionic bond, you get an ionic
compound.
● The positive and negative charges balance exactly, so the total overall
charge of an ionic compound is zero.
Factors affecting ionic bonding:
1. Ionic Radius - smaller ions can pack more closely together than larger
ions, and since electrostatic attraction gets weaker with distance, small
and closely-packed ions have stronger ionic bonding than larger ions,
and will also have higher melting/boiling points.
2. Ionic Charge - the greater the charge on an ion, the stronger the ionic
bond and therefore the higher the melting/boiling point.
Trends in ionic radii:
1. Ionic radius - increases down a group, as extra electron shells are
added.
2. Isoelectronic ions - these are ions of different atoms with the same
number of electrons (e.g. O2- and Na+). The ionic radius of a set of
isoelectronic ions decreases as the atomic number increases. This is
because the electrons are more strongly attracted to the nucleus with
more protons, so they are pulled in a little.
Dot-and-cross diagrams:
● Show the arrangement of electrons in an atom or ion, and they can also
show where the electrons in a bond originally came from.
● Usually only the outer electrons are shown.
Recap:
● When electrons are transferred, ions are formed.
● They can be positive cations or negative anions.
● Simplest ions are single atoms which have achieved a full outer shell.
● Elements will lose or gain electrons to get the full outer shell, and will
therefore form an ion with the same charge (e.g. Mg will lose 2
electrons and become Mg2+).
Ionic Bonding:
● This is the strong electrostatic attraction between oppositely charged
ions.
● The stronger the electrostatic attraction, the stronger the ionic bond.
● When oppositely charged ions form an ionic bond, you get an ionic
compound.
● The positive and negative charges balance exactly, so the total overall
charge of an ionic compound is zero.
Factors affecting ionic bonding:
1. Ionic Radius - smaller ions can pack more closely together than larger
ions, and since electrostatic attraction gets weaker with distance, small
and closely-packed ions have stronger ionic bonding than larger ions,
and will also have higher melting/boiling points.
2. Ionic Charge - the greater the charge on an ion, the stronger the ionic
bond and therefore the higher the melting/boiling point.
Trends in ionic radii:
1. Ionic radius - increases down a group, as extra electron shells are
added.
2. Isoelectronic ions - these are ions of different atoms with the same
number of electrons (e.g. O2- and Na+). The ionic radius of a set of
isoelectronic ions decreases as the atomic number increases. This is
because the electrons are more strongly attracted to the nucleus with
more protons, so they are pulled in a little.
Dot-and-cross diagrams:
● Show the arrangement of electrons in an atom or ion, and they can also
show where the electrons in a bond originally came from.
● Usually only the outer electrons are shown.
