Unit 1 – Bonding
Bonding
Compounds are atoms of different elements bonded together:
1. When different elements join or bond together, this forms a compound.
2. In compounds, there are two types of bonding.
- Ionic
- Covalent
The four types of crystal structure:
- ionic
- metallic
- macromolecular (giant covalent)
- molecular.
The structures of the following crystals as examples of these four types of crystal
structure:
- diamond
- graphite
- ice
- iodine
- magnesium
- sodium chloride.
Ionic Bonding
Ionic Bonding is when ions are held together by electrostatic forces of attraction.
Ions are formed when one or more electrons are transferred from one atom to
another.
E.G Na Na+ + e- = The sodium atom loose’s 1 electron to form a 1+ sodium
ion.
E.G Cl + e- Cl- = The chlorine atom gains 1 electron to form 1+ chloride ion.
• Elements in the same group all have the same number of outer electrons.
They have to loose or gain electrons so they can get the full outer shell
they desire. This therefore means they form ions with the same charges.
• Electrostatic attraction holds positive and negative ions together. It is a
very strong force. This known as ionic bonding.
Compound Ions
This is where lots of ions are made up of groups of atoms with an overall charge.
- SO42-
, - OH-
- NO3-
- CO32-
- NH4+
Working out the formula of ionic compounds
Ionic compounds can be positively charged and negatively charged.
The overall charge of an atom is zero. This means the negative charges in the
compound must balance all the positive charges.
Sodium Nitrate = Na+ and NO3-. These charges are balanced with one of each ion
therefore = NaNO3
Magnesium Chloride = Mg2+ and Cl-. As a chloride ion has a 1- charge we will need
to balance out the charge of the 2+ Magnesium ion = MgCl2.
Sodium Chloride has a giant ionic lattice structure:
Ionic crystals are giant lattices on ions. A lattice is just a regular structure. The
structure is ‘giant’ as its made up of the same basic unit repeated over and over.
It is a cube shape and different ionic compounds have different shaped structures
however, they are all still different shaped structures, by their all giant lattices.
Ionic Structure explains the behaviour of ionic compounds:
1. Ionic compounds conduct electricity when they’re molten or dissolved.
2. They have high melting points – Giant ionic lattices are held together by
strong electrostatic forces. It takes a lot of energy to overcome these forces,
so melting points are high. There are 1000s strong ionic bonds to break.
3. Ionic compounds tend to dissolve in water. Water molecules are polar
where part of it has a small negative charge and other bits have small
positive charges. These charge particles pull ions away from the lattice,
causing it to dissolve.
Examples:
Sodium chloride is an ionic compound, therefore when the compound is solid, the
ions aren’t able to move and carry a charge through the structure so it doesn’t
conduct electricity.
Sea water conducts electricity as its dissolved in water which means its ions are
free to move and carry a charge.
Magnesium oxide has a higher melting point than sodium chloride as there is a
stronger force of attraction between the ions.
Bonding
Compounds are atoms of different elements bonded together:
1. When different elements join or bond together, this forms a compound.
2. In compounds, there are two types of bonding.
- Ionic
- Covalent
The four types of crystal structure:
- ionic
- metallic
- macromolecular (giant covalent)
- molecular.
The structures of the following crystals as examples of these four types of crystal
structure:
- diamond
- graphite
- ice
- iodine
- magnesium
- sodium chloride.
Ionic Bonding
Ionic Bonding is when ions are held together by electrostatic forces of attraction.
Ions are formed when one or more electrons are transferred from one atom to
another.
E.G Na Na+ + e- = The sodium atom loose’s 1 electron to form a 1+ sodium
ion.
E.G Cl + e- Cl- = The chlorine atom gains 1 electron to form 1+ chloride ion.
• Elements in the same group all have the same number of outer electrons.
They have to loose or gain electrons so they can get the full outer shell
they desire. This therefore means they form ions with the same charges.
• Electrostatic attraction holds positive and negative ions together. It is a
very strong force. This known as ionic bonding.
Compound Ions
This is where lots of ions are made up of groups of atoms with an overall charge.
- SO42-
, - OH-
- NO3-
- CO32-
- NH4+
Working out the formula of ionic compounds
Ionic compounds can be positively charged and negatively charged.
The overall charge of an atom is zero. This means the negative charges in the
compound must balance all the positive charges.
Sodium Nitrate = Na+ and NO3-. These charges are balanced with one of each ion
therefore = NaNO3
Magnesium Chloride = Mg2+ and Cl-. As a chloride ion has a 1- charge we will need
to balance out the charge of the 2+ Magnesium ion = MgCl2.
Sodium Chloride has a giant ionic lattice structure:
Ionic crystals are giant lattices on ions. A lattice is just a regular structure. The
structure is ‘giant’ as its made up of the same basic unit repeated over and over.
It is a cube shape and different ionic compounds have different shaped structures
however, they are all still different shaped structures, by their all giant lattices.
Ionic Structure explains the behaviour of ionic compounds:
1. Ionic compounds conduct electricity when they’re molten or dissolved.
2. They have high melting points – Giant ionic lattices are held together by
strong electrostatic forces. It takes a lot of energy to overcome these forces,
so melting points are high. There are 1000s strong ionic bonds to break.
3. Ionic compounds tend to dissolve in water. Water molecules are polar
where part of it has a small negative charge and other bits have small
positive charges. These charge particles pull ions away from the lattice,
causing it to dissolve.
Examples:
Sodium chloride is an ionic compound, therefore when the compound is solid, the
ions aren’t able to move and carry a charge through the structure so it doesn’t
conduct electricity.
Sea water conducts electricity as its dissolved in water which means its ions are
free to move and carry a charge.
Magnesium oxide has a higher melting point than sodium chloride as there is a
stronger force of attraction between the ions.
