C2 Bonding, structure and the properties of matter Flashcards
Describe fullerenes and give a named example.
Fullerenes are molecules of carbon atoms with hollow shapes.
The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms.
The first fullerene to be discovered was buckminsterfullerene (C60) which has a spherical shape.
Describe the bonding in diamond and some of its properties.
In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard, has a very high melting point and does not conduct electricity.
Polymers have very strong covalent bonds between atoms, true or false?
TRUE! Atoms in polymers are held in palce by strong covalent bonds.
Describe what a monomer looks like.
A monomer is an unsaturated compound with a double bond.
Explain why polymer molecules are solids at room temperature.
Polymer molecules are solid at room temperature because they have relatively strong intermolecular forces between polymer chains.
Describe the structure of graphene and give one use of this material.
Graphene is made up of a single layer of graphite. It can be used in electrical circuits.
What are carbon nanotubes and why are they useful?
Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials.
Describe the bonding in graphite.
In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers.
In graphite, one electron from each carbon atom is delocalised.
What are the three states of matter?
The three states of matter are solid, liquid and gas.
List the state symbols used in chemical equations.
- Solid (s)
- Liquid (l)
- Gas (g)
- Aqueous (aq)
Aqueous means the substance is dissolved in water.
Describe some of the physical properties of small molecules.
Small molecules are usually gases or liquids that have relatively low melting points and boiling points.
What determines the melting and boiling point of substances?
The melting and boiling points of substances are determined by the forces between the particles.
This depends upon the structure and bonding within the substance.
What is the pattern in melting and boiling points as molecule size gets bigger?
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
Do metals lose or gain electrons?
Metals lose electrons.
Do non metals lose or gain electrons?
Non metals gain electrons.
What is the charge of a metal ion?
The charge of a metal ion is positive.
What is the charge of a non-metal ion?
The charge of a non-metal ion is negative.
What is an ionic bond?
An ionic bond is the strong electrostatic force of attraction between oppositely charged ions
What are the three types of chemical bonds?
The three types of chemical bonds are ionic bonds, covalent bonds and metallic bonds.
Describe the the strength of the intermolecular forces between small molecules.
Small molecules have only weak forces between the molecules (intermolecular forces).
It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.
Where do ionic bonds form?
Ionic bonds form between metals and non-metals.
Where do covalent bonds form?
Covalent bonds form between non-metal atoms.
What is an ionic compound and how are ions held together?
An ionic compound is a giant lattice structure.
Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions.
What is a giant ionic lattice?
A giant ionic lattice is made up of oppositely charged ions held together by electrostatic forces acting in all directions. This is called ionic bonding.
What does the picture of the giant ionic lattice of sodium chloride look like?
Draw a dot and cross diagram showing the formation of NaCl. Include electronic configurations.
Why do ionic compunds conduct electricity when molten or dissolved, but not when solid?
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow
(because dissolving ionic compounds breaks up lattice structure)
Why do ionic compounds have high melting points?
Ionic bonding produces ions which are held together by strong electrostatic forces of attraction (ionic bonds)
Ions are held in a giant lattice structure
There are many strong bonds to break
Large amounts of energy needed to overcome these strong bonds.
Ionic bonding involves the transfer of what?
Ionic Bonding involves the transfer of electrons.
What is a covalent bond?
A covalent bond is the strong electrostatic atraction between the positive nuclei and the shared paris of electrons
Do small covalent molecules conduct electricity?
No, small covalent molecules do not conduct electricity as there is no overall charge or spare ions or electrons to carry a charge.
Giant covalent structures are solids with high melting points. Expalin why.
Giant covalent compounds are solids with high metling points because the atoms are held together by strong covalent bonds that require large amounts of energy to break them.
Describe the properties of graphite in relation to its structure.
Graphite is soft and slippery becuase of the weak intermolecular forces between layers.
The delocalised electrons allow graphite to carry an electrical charge so it conducts electricity.
Give three examples of giant covalent structures.
Three examples of giant covalent structures are diamond, graphite and silicon dioxide.
What are the particles involved with metallic bonding?
For metallic bonding the particles are atoms which share delocalised electrons.
Why do metals conduct electricity.
Metals conduct electricity because delocalised electrons are free to carry the electrical charge.
Pure metals can be bent or drawn into wires. What are the names given to these properties?
Metals that can be bent are called malleable.
Metals that can be drawn into wires are called ductile.
How are pure metals made harder?
Pure metals are made harder by combining them with other metals to make alloys.
What are simple molecular structures?
Composed of small molecules that contain relatively few atoms with weak intemrolecular forces betwene the molecules
What are giant covalent structures?
Made from a huge number of atoms all covalently bonded together
What are the properties of simple covalent molecules?
- Low melting and boiling points
- Do not conduct electricity
- Intermolecular forces get stronger with the size of the atom
Why do simple covalent molecules not conduct electricity even when they are molten or dissolved?
They do not contain any free ions or electrons that can carry the charge
What is an allotrope?
Pure forms of the same element but have different structures
(Q) Explain what the formula ‘MgO’ means (3)
One magnesium atom reacts with one oxygen atom and electrons are transferred.
A magnesium atom loses 2 electrons to form a Mg 2+ ion.
The oxygen atom gains 2 electrons to form an O 2- ion.
These oppositely charged ions are held together by strong ionic bonds.
(Q) What are the advantages and disadvantages of the 2D ball and stick model?
Advantages:
- Shows the atoms bonded to each other
Disadvantages:
- Does not show the shape of the molecule
(Q) Suggest why alloys do not conduct electricity as well as pure metals (2)
Alloys have an irregular arrangement and contains different types of atoms that are of different sizes which disrupts the layers.
This means that delocalised electrons cannot move through the alloy as freely to carry charge as they can in a pure metal.
(Q) Metals have stong metallic bonding which makes them have high melting and boiling points. Explain why.
Strong metallic bonds are held together by strong forces of attraction between positive metal cations and delocalised electrons.
They need lots of energy to be broken.
(Q) What are the advantages and disadvantages of the 3D ball and stick model?
Advantages:
- Shows the shape of the molecule
Disadvantages:
- Does not show it is bonded via electrons
- (FOR Qs) Not a true representation of the structure of compounds since there are no gaps or sticks between the ions in reality.
(Q) What are the advantages and disadvantages of the dot and cross diagram?
Advantages:
- Shows electrons for each atom
Disadvantage:
- It is a 2D representation
(Q) Explain why chlorine is a gas at room temperature, but sodium chloride is a solid at room temperature
Chlorine is a gas because:
- it is a simple molecular structure
- forces between the molecules are weak
- so they have low melting / boiling points
- because less energy is needed to overcome the weak forces
Sodium chloride is a solid because
- has ionic bonds (strong electrostatic forces of attraction) between oppositely charged ions in all directions
- forming a giant lattice structure
- so high melting / boiling points
- because lots of energy is needed to break the bonds
(Q) Explain why CO2 has a very low boiling point
Carbon dioxide is a simple molecular structure.
There are weak intermolecular forces of attraction between the molecules therefore little energy is needed to overcome these forces.
(Q) Explain why nanotubes are strong
Strong covalent bonds between carbon atoms
(Q) Would you expect sodium chloride or potassium chloride to have a higher melting point?
Sodium chloride because
- ions have the same charge so there is the same electrostatic forces between particles
- soidum ions are smaller however, so the forces have a larger effect
(Q) Describe what happens when two atoms of potassium react with one atom of sulfur
- 2 electrons are transferred from 2 potassium atoms to 1 sulfur atom.
- Each potassium atom loses 1 electrons to form a completed outer shell which forms a positive K + ion.
- The sulfur atom gains 2 electrons to form a completed outershell to form a negative S 2- ion.
- These oppositely charged ions are held together by strong electrostatic forces of attraction.
- The solid ionic compound formed is potassium sulfide (K2S)
