Chemistry – Key Topic 2
4.2 Bonding, structure, and the properties of matter
4.2.1 Chemical bonds, ionic, covalent and metallic
4.2.1.1 Chemical bonds
There are three type of strong chemical bonds : ionic, covalent and metallic. For ionic
bonding the particle are oppositely charged ions. For covalent bonding the particles
are atoms which share pairs of electrons. For metallic bonding the particles are atoms
which share delocalised electrons
Ionic bonding occurs in compounds formed from metals combined with non-metals
Covalent bonding occurs in most non-metallic elements and in compounds of non-
metals
Metallic bonding occurs in metallic elements and alloys
4.2.1.2 Ionic bonding
When a metal atom reacts with a non-metal atom electrons in the outer shell of the
metal atom are transferred. Metal atoms lose electrons to become positively charged
ions. Non-metal atoms gain electrons to become negatively charged ions. The ions
produced by metals in groups 1 and 2 and by non-metals in groups 6 and 7 have the
electronic structure of that of a noble gas (group 0)
- Groups 1,2,6,7 are the ones that most readily form ions. Groups 1 and 2 are
metals that lose electrons to form positive ions (cations) and groups 6 and 7 are
non-metals that gain electrons to form negative ions (anions)
The electron transfer during the formation of an ionic compound can be represented
by a dot and cross diagram.
- This shows the arrangement of electrons in an atom or ion. The diagrams can
show which atom the electrons in an ion originally came from, since they are
represented by dots and crosses.
- Limitations of this is that it fails to illustrate the 3D arrangements of the atoms
and electron shells. They don’t show the structure of the compound, the size of
the ions or how they are arranged.
The charge on the ions produced by metals in groups 1 and 2 and by non-metals in
groups 6 and 7 relates to the group number of the element in the periodic table
4.2.1.3 Ionic compounds
An ionic compound is a giant structure of ions. Ionic compounds are held together by
strong electrostatic forces of attraction between oppositely charged ions of a metal
and non-metal – This attraction is called an ionic bond
, These forces act in all directions in the giant ionic lattice and this is called ionic
bonding. The metal loses the electron to form a positive ion and the non-metal gains
this to become a negative ion (electrons are transferred from metal atoms to non
metal atoms to form ions with group 0 electron structures)
Properties: Higher melting point, because it takes a large amount of energy to break
the many strong electrostatic forces of attraction between the many oppositely
charged ions In the giant ionic lattice. Conductors of electricity (When molten or
dissolved in water) because the ions are free to move so electric charge can flow.
- Some ionic compounds also dissolve easily in water. The ions separate and are all
free to move in the solution, so they’ll carry charge
4.2.1.4 Covalent bonding
Covalent bonding is the electrostatic attraction between the shared pairs of electrons
and the positive nuclei within two non-metals. The bonds are very strong
- Covalently bonded substances may consist of small molecules
- Some covalently bonded substances have very large molecules , such as polymers.
- Some covalently bonded substances have giant covalent structures, such as
diamond and silicon dioxide
Each atom involved generally makes enough covalent bonds to fill up its outer shell.
Having a full outer shell gives it the electronic structure of a noble gas, which is very
stable
It happens in compounds of non-metals (H2O) and in non-metals (Cl2)
You can use dot and cross diagrams to show the bonding in covalent compounds,
with electrons drawn in the overlap between the outer orbitals of two atoms (the
shared electrons)
- they show which atom the electrons in a covalent bond came from, but not the
relative sizes of the atoms, or how the atoms are arranged in space.
You can use a displayed formula, showing the covalent bonds as lines between atoms.
- this shows how atoms are connected in large molecules, but they don’t show the 3D
structure of the molecule or which atoms the electrons in the covalent bond have
come from
You can use a 3D model, showing the atoms, the covalent bonds and their
arrangement in space next to each other.
- but they can get confusing for large molecules where there are lots of atoms to
include. They don’t show where the electrons in the bonds have come from either
4.2 Bonding, structure, and the properties of matter
4.2.1 Chemical bonds, ionic, covalent and metallic
4.2.1.1 Chemical bonds
There are three type of strong chemical bonds : ionic, covalent and metallic. For ionic
bonding the particle are oppositely charged ions. For covalent bonding the particles
are atoms which share pairs of electrons. For metallic bonding the particles are atoms
which share delocalised electrons
Ionic bonding occurs in compounds formed from metals combined with non-metals
Covalent bonding occurs in most non-metallic elements and in compounds of non-
metals
Metallic bonding occurs in metallic elements and alloys
4.2.1.2 Ionic bonding
When a metal atom reacts with a non-metal atom electrons in the outer shell of the
metal atom are transferred. Metal atoms lose electrons to become positively charged
ions. Non-metal atoms gain electrons to become negatively charged ions. The ions
produced by metals in groups 1 and 2 and by non-metals in groups 6 and 7 have the
electronic structure of that of a noble gas (group 0)
- Groups 1,2,6,7 are the ones that most readily form ions. Groups 1 and 2 are
metals that lose electrons to form positive ions (cations) and groups 6 and 7 are
non-metals that gain electrons to form negative ions (anions)
The electron transfer during the formation of an ionic compound can be represented
by a dot and cross diagram.
- This shows the arrangement of electrons in an atom or ion. The diagrams can
show which atom the electrons in an ion originally came from, since they are
represented by dots and crosses.
- Limitations of this is that it fails to illustrate the 3D arrangements of the atoms
and electron shells. They don’t show the structure of the compound, the size of
the ions or how they are arranged.
The charge on the ions produced by metals in groups 1 and 2 and by non-metals in
groups 6 and 7 relates to the group number of the element in the periodic table
4.2.1.3 Ionic compounds
An ionic compound is a giant structure of ions. Ionic compounds are held together by
strong electrostatic forces of attraction between oppositely charged ions of a metal
and non-metal – This attraction is called an ionic bond
, These forces act in all directions in the giant ionic lattice and this is called ionic
bonding. The metal loses the electron to form a positive ion and the non-metal gains
this to become a negative ion (electrons are transferred from metal atoms to non
metal atoms to form ions with group 0 electron structures)
Properties: Higher melting point, because it takes a large amount of energy to break
the many strong electrostatic forces of attraction between the many oppositely
charged ions In the giant ionic lattice. Conductors of electricity (When molten or
dissolved in water) because the ions are free to move so electric charge can flow.
- Some ionic compounds also dissolve easily in water. The ions separate and are all
free to move in the solution, so they’ll carry charge
4.2.1.4 Covalent bonding
Covalent bonding is the electrostatic attraction between the shared pairs of electrons
and the positive nuclei within two non-metals. The bonds are very strong
- Covalently bonded substances may consist of small molecules
- Some covalently bonded substances have very large molecules , such as polymers.
- Some covalently bonded substances have giant covalent structures, such as
diamond and silicon dioxide
Each atom involved generally makes enough covalent bonds to fill up its outer shell.
Having a full outer shell gives it the electronic structure of a noble gas, which is very
stable
It happens in compounds of non-metals (H2O) and in non-metals (Cl2)
You can use dot and cross diagrams to show the bonding in covalent compounds,
with electrons drawn in the overlap between the outer orbitals of two atoms (the
shared electrons)
- they show which atom the electrons in a covalent bond came from, but not the
relative sizes of the atoms, or how the atoms are arranged in space.
You can use a displayed formula, showing the covalent bonds as lines between atoms.
- this shows how atoms are connected in large molecules, but they don’t show the 3D
structure of the molecule or which atoms the electrons in the covalent bond have
come from
You can use a 3D model, showing the atoms, the covalent bonds and their
arrangement in space next to each other.
- but they can get confusing for large molecules where there are lots of atoms to
include. They don’t show where the electrons in the bonds have come from either
