C2 Flashcards
What are the three types of strong chemical bonds?
Ionic, covalent and metallic
What does ionic bonding involve in terms of particles?
Oppositely charged ions.
What does covalent bonding involve in terms of particles?
Atoms which share pairs of electrons
What does metallic bonding involve in terms of particles?
Atoms which share delocalised electrons.
When does ionic bonding occur?
In compounds formed from metals combined with non-metals.
When does covalent bonding occur?
In most non-metallic elements and in compounds of non-metals
When does metallic bonding occur?
In metallic elements and alloys.
Explain chemical bonding in terms of electrostatic forces and the transfer or sharing of electrons.
- A chemical bond is a lasting attraction between atoms,ions or molecules that enables the formation of chemical compounds.
- The bond may result from the electrostatic force between oppositely charged ions as in ion bonds or through the sharing of electrons as in covalent bonds
When a metal atom reacts with a non-metal atom what is transferred?
Electrons in the outer shell of the metal atom are transferred
Why do metal atoms lose electrons?
To become positively charged ions.
Why do non-metals lose electrons?
Non-metal atoms gain electrons to become negatively charged ions
What are the ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 similar to in terms of electronic structure?
They have the electronic structure of a noble gas (Group 0)
How can the electron transfer during the formation of an ionic compound be represented?
By a dot and cross diagram
Note:
AQA says that students should be able to draw dot and cross diagrams for ionic compounds formed by metals in Groups 1 and 2 with non-metals in Groups 6 and 7
(Check page 115)
What does the charge on the ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 relate to?
The group number of the element in the periodic table.
Note:
AQA says that students should be able to work out the charge on the ions of metals and non-metals from the group number of the element, limited to the metals in Groups 1 and 2, and non-metals in Groups 6 and 7.
What is an ionic bond?
When a metal or nonmetal react together, the metal atom loses electrons to form a positively charged ion and a non-metal gains these electrons to form a negatively charged ion. These oppositely charged ions are strongly attracted to one another by electrostatic forces.
What is an ionic compound?
An ionic compound is a giant structure of ions. Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding.
What is the structure of a single crystal of sodium chloride (table salt)
One giant ionic lattice. The Na+ and Cl- ions are held together in a regular lattice
(Check CGP 114 to see its structure in a diagram)
Note:
Students should be able to:
- deduce that a compound is ionic from a diagram of its
structure in one of the specified forms - describe the limitations of using dot and cross, ball and stick,
two and three-dimensional diagrams to represent a giant ionic
structure - work out the empirical formula of an ionic compound from a
given model or diagram that shows the ions in the structure. - Students should be familiar with the structure of sodium chloride but
do not need to know the structures of other ionic compounds.
What are covalent bonds?
- When atoms share pairs of electrons, they form covalent bonds.
- These bonds between atoms are strong.
What may covalently bonded substances consist of?
Small molecules
Note:
AQA says that students should be able to recognise common substances that
consist of small molecules from their chemical formula.
(Check CGP page 116)
What are some covalently bonded substances like?
- They have very large molecules, such as polymers and they have giant covalent structures
- Diamond and silicon dioxide have giant covalent structures
Note:
The covalent bonds in molecules and giant structures can be
represented in the following forms (Check CGP page 115 for this)
Note:
AQA says that students should be able to:
- draw dot and cross diagrams for the molecules of hydrogen,
chlorine, oxygen, nitrogen, hydrogen chloride, water,
ammonia and methane - represent the covalent bonds in small molecules, in the
repeating units of polymers and in part of giant covalent
structures, using a line to represent a single bond - describe the limitations of using dot and cross, ball and stick,
two and three-dimensional diagrams to represent molecules
or giant structures - deduce the molecular formula of a substance from a given
model or diagram in these forms showing the atoms and
bonds in the molecule.
What is metals structure?
Metals consist of giant structures of atoms arranged in a regular
pattern
State the characteristics of metals
- The electrons in the outer shell of metal atoms are delocalised
- So they are free to move through the whole structure.
- The sharing of delocalised electrons gives rise to strong metallic bonds
Note:
The bonding in metals may be represented in the following form(Check page 119)
What are the three states of matter?
Solid, metals and gases
What is the particle theory?
- The particle theory of matter is a model that describes the arrangement and movement of particles in a substance.
- The model is used to explain the physical properties of solids, liquids and gases
How can the three states of matter be represented?
- The three states of matter can be represented by a simple model.
- In this model, particles are represented by small solid spheres.
- Particle theory can help to explain melting, boiling, freezing and
condensing.
(Check CGP page 120)
What does the amount of energy needed to change state from solid to liquid
and from liquid to gas depend on?
The strength of the forces between the particles of the substance
What does the nature of the particles involved depends on for changing state?
- The type of bonding and the structure of the substance.
- This is because the stronger the forces between the particles the higher the melting point and boiling point of the substance.
What are the limitations of the simple model for demonstrating how the three states of matter look?
Limitations of the simple model above include:
- In the model there are no forces
- That all particles are represented as spheres
- The spheres are solid
Note:
AQA says that students should be able to:
- predict the states of substances at different temperatures
given appropriate data - explain the different temperatures at which changes of state
occur in terms of energy transfers and types of bonding - recognise that atoms themselves do not have the bulk
properties of materials - explain the limitations of the particle theory in
relation to changes of state when particles are represented by
solid inelastic spheres which have no forces between them.
What are the chemical symbols for equations?
S - Solid
L - Liquid
G - Gas
Aq - Aqueous
Note:
AQA says that students should be able to include appropriate state symbols in chemical equations for the reactions in this specification.
What is the structure of an ionic compound?
Ionic compounds have regular structures (giant ionic lattices) in
which there are strong electrostatic forces of attraction in all
directions between oppositely charged ions
Why do ionic compounds have high melting and boiling points?
- These compounds have high melting points and high boiling points
- This is because of the large amounts of energy needed to break the many strong bonds
When ionic compounds are melting or dissolved in water, what happens?
- When melted or dissolved in water, ionic compounds conduct
electricity - This is because the ions are free to move and so charge can
flow.
What are substances that consist of small molecules like and what are their characteristics?
Substances that consist of small molecules are usually gases or
liquids that have relatively low melting points and boiling points
What do substances that consist of small molecules have weak forces between the molecules?
- These substances 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
What do intermolecular forces increase with?
- The intermolecular forces increase with the size of the molecules
- So larger molecules have higher melting and boiling points.
Why do substances that consist of small molecules not conduct electricity?
These substances do not conduct electricity because the molecules do not have an overall electric charge
Note:
AQA says that students should be able to use the idea that intermolecular forces are weak compared with covalent bonds to explain the bulk properties of molecular substances
What is a polymer?
A polymer is a large molecule made up of repeating subunits known as monomers
What are the characteristics of a polymer?
- Polymers have very large molecules.
- The atoms in the polymer molecules are linked to other atoms by strong covalent bonds.
- The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
Note:
AQA says that students should be able to recognise polymers from diagrams showing their bonding and structure
(Check CGP page 117)
What are giant covalent structures?
Macromolecules
What are substances that consist of giant covalent structures like?
Substances that consist of giant covalent structures are solids with
very high melting points
How are giant covalent structures bonded?
All atoms are bonded to each other by strong covalent bonds
What is the melting and boiling point of giant covalent structures?
They have very high melting and boiling points as lots of energy is needed to break the covalent bonds between the atoms
State examples of giant covalent structures
Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures
What do most giant covalent structures not contain?
They don’t contain charged particles, so they don’t conduct electricity - not even when molten (except for a few weird exceptions such as graphite)
Note:
AQA says that students should be able to recognise giant covalent structures from diagrams showing their bonding and structure.
What is metals structure in terms of atoms and what does this lead to?
- Metals have giant structures of atoms with strong metallic bonding.
- This means that most metals have high melting and boiling points
How are atoms arranged in pure metal and what does this lead to?
- In pure metals, atoms are arranged in layers, which allows metals to be bent and shaped.
- Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder
Why are alloys harder than pure metals in terms of distortion of the layers of atoms in the structure of a pure metal?
- As pure metals are often too soft when they are pure so they are mixed with other metals to make them harder.
- Alloys are harder than pure metals which makes it more useful
What is an alloy?
A mixture of two or more metals or a metal and another element
Why are metals good conductors of electricity?
- Metals are good conductors of electricity because the delocalised
electrons in the metal carry electrical charge through the metal. - Metals are good conductors of thermal energy because energy is
transferred by the delocalised electrons.
What is the structure of diamond and what does this lead to?
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.
What is the structure of graphite and what does this lead to?
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.
Note:
AQA says that students should be able to:
- Explain the properties of graphite in terms of its structure and bonding.
- Know that graphite is similar to metals in that it has delocalised electrons.
What is graphene?
Graphene is a single layer of graphite and has properties that make it useful in electronics and composites.
State the properties of graphene in terms of its structure and bonding
- Graphene is a single-atom thick layer of graphite with strong covalent bonds between each carbon atom.
- The atoms arranged in hexagons.
The things above are the reason why graphene has high melting and boiling points
What is fullerenes and what is its structure?
- 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
What was the first fullerene to be discovered?
The first fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape.
What are carbon nanotubes?
- Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios.
- Their properties make them useful for nanotechnology, electronics and materials.
Note:
AQA says that students should be able to:
- recognise graphene and fullerenes from diagrams and
descriptions of their bonding and structure - give examples of the uses of fullerenes, including carbon
nanotubes.
