C2 Bonding, Structure and the Properties of Matter Flashcards
What is ionic bonding?
lonic bonding is the electrostatic attraction between positive and negative ions.
It is a relatively strong attraction.
How are ionic compounds held together?
- They are held together ni a giant lattice.
- It’s a regular structure that extends in all directions in a
substance. - Electrostatic attraction between positive and negative ions holds the structure together.
State properties of ionic substances
- High melting and boiling point (strong electrostatic forces between oppositely charged ions)
- Do not conduct electricity when solid (ions in fixed positions).
- Conduct when molten or dissolved in water - ions are free to move.
Give 5 examples of positive ions and 5 examples of negative ions (give names of negative anions). What is important when working out a formula of an ionic compound?
E.g. Positive: Na=, Mg2+, Al3+, Ca2=, Rb+
E.g. Negative: Cl-, Br-, SO4 2-, NO3-, OH- (chloride, bromide, sulFate, nitrate)
lonic compounds are electrically neutral, i.e. positive and negative charges balance each other.
How are ionic compounds formed? Explain in terms of MgO case.
Reaction of a metal with a non-metal.
Electron transfer occurs - metal gives away its outer shell electrons to non-metal.
Mg is in Group Il, so has 2 available outer shell electrons.
O is in Group VI, so can accept 2 electrons to get a full outer shell configuration.
Mg becomes M2+ and O becomes 02- (oxide)
What is a covalent bond?
Covalent bond is a shared pair of electrons between two atoms.
Describe the structure and properties of simple molecular covalent substances
- Do not conduct electricity (no ions)
- Small molecules
- Weak intermolecular forces, therefore:
- Low melting and boiling points
How do intermolecular forces change as the mass/size of the molecule increases?
They increase. That causes melting/boiling points to increase as well (more energy needed to overcome these forces).
What are polymers? What are thermosoftening polymers?
Polymers are very large molecules (>100s, 1000s of atoms) with atoms linked by covalent bonds.
Thermosoftening polymers - special type of polymers; they melt/soften when heated. There are no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature. These forces are overcome with heating - polymer melts.
What are giant covalent substances? Give examples
- Solids, atoms covalently bonded together ni a giant lattice.
- High melting/boiling points - strong covalent bonds.
- Mostly don’t conduct electricity (no delocalised e )
- Diamond, graphite, silicon dioxide.
List the allotropes of carbon.
- Diamond
- Graphite
- Fullerenes
- Nanotubes
- Graphene
Describe and explain the properties of allotropes of carbon. (DIAMOND)
- four, strong covalent bonds for each carbon atom
- very hard (Strong bonds)
- very high melting point (strong bonds)
- does not conduct (no delocalised electrons)
Describe and explain the properties of allotropes of carbon. (GRAPHITE)
- three covalent bonds for each carbon atom
- layers of hexagonal rings
- high melting point
- layers free to slide as weak intermolecular forces between layers; soft, can be used as a lubricant
- conduct thermal and electricity due to one delocalised electron per each carbon atom
Describe and explain the properties of allotropes of carbon. (GRAPHENE)
- a single layer of graphite
Describe and explain the properties of allotropes of carbon. (FULLERENES)
- holow shaped molecules
- based on hexagonal rings but may have 5/7-carbon rings
- C60 has spherical shape, simple molecular structure (Buckminsterfullerene)
Describe and explain the properties of allotropes of carbon. (NANOTUBES)
- cylindrical fullerene with high length to diameter ratio
- High tensile strength (strong bonds)
- Conductivity (delocalised electrons)
What is metallic bonding?
Forces of attraction between delocalised electrons and nuclei of metal ions.
Describe properties of metals
- High melting/boiling points (strong forces of attraction)
- Good conductors of heat and electricity (delocalised electrons)
- Malleable, soft (layers of atoms can slide over each other whilst maintaining
the attraction forces)
What are alloys? Why are they harder than pure metals?
Alloys:
- mixtures of metal with other elements, usually metals
- different sizes of atoms distorts the layers, so they can’t slide over each other,
therefore aloys are harder than pure metals
What are covalent bonds made out of
Two non metallic atoms
The sharing of pairs of electrons between atoms and other covalent bonds.
Simple Covalent bonds properties
Boiling/Melting points
- low: because of weak intermolecular forces between molecules
Conductivity when solid
- poor: no ions to conduct
Conductivity when molten
- poor: no ions
General description
- mostly gases and liquids
What are ionic bonds made out of
Between a metal and non-metal
The electrostatic attraction between oppositely charged ions in a chemical compound
Ionic bonds properties
Boiling/Melting points
- high: because of giant lattice of ions with strong forces between oppositely charged ions
Conductivity when solid
- poor: ions can’t move
Conductivity when molten
- good: ions are free to move
General description
- crystalline solids
What are giant covalent bonds made out of
Sometimes, atoms of certain elements come together to form a giant molecule which is made up of millions of atoms.
Examples of giant covalent structures are Diamond, Graphite, and Silicon Dioxide.
Giant Covalent bonds properties
Boiling/Melting points
- high: because of many strong covalent bonds between atoms in giant structure
Conductivity when solid
- diamond and sand: poor, because electrons can’t move
- graphite: good as free delocalised electrons between layers can move through structure
Conductivity when molten
- poor
General description
- solids
What are metallic bonds made out of
The electrostatic attraction between metal cations and delocalised electrons.
Metallic bonds properties
Boiling/Melting points
- high: strong electrostatic forces between positive ions ad delocalised electrons
Conductivity when solid
- good: delocalised electrons are free to move through structure
Conductivity when molten
- good
General description
- shiny metal solids
What are the limitations of the simple model?
There are no forces between spheres and atoms, molecules and ions are solid spheres - this is not true
What does the amount of energy needed to change state from solid to liquid or liquid to gas depend on?
The strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance
A pure substance wil melt or boil at..?
A fixed temperature.
A mixture will melt over a range of temperatures.
What are the three states of matter?
Solid, liquid and gas
What is nanoscience?
Science that studies particles that are 1-100nm in size
State the uses of nanoparticles
- Medicine (drug delivery systems)
- Electronics
- Deodorants
- Sun creams (better skin coverage and move effective protection against cell damage)
What are fine and coarse particles?
- Fine particles (soot), 100-2500 nm diameter
- Coarse particles (dust), 2500-10^5 nm diameter
Conductor:
A material which contains charged particles which are free to move to carry electrical or thermal energy.
Covalent bond:
A shared pair of electrons between two non-metals.
Diamond:
A giant covalent structure which is made up of carbon atoms each of which form
four covalent bonds with four other carbon atoms.
Electrostatic forces:
The strong forces of attraction between oppositely charged ions.
Empirical formula:
The smallest whole number ratio of atoms of each element in a compound.
Fullerenes:
Fullerenes are molecules of carbon atoms with hollow shapes. The structures are based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms.
Gas:
The state of matter where the particles have the most energy. The particles in a gas are relatively spread out and move randomly in all directions.
Graphene:
A single layer of graphite with properties that make it useful in electronics and composites.
Graphite:
A giant covalent structure which is made up of carbon atoms each of which form three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers.
Ionic bond:
A metal atom loses electron(s) to form a positively charged ion and a non-metal gains these electron(s) to form a negatively charged ion. An ionic bond is formed between the oppositely charged ions.
Ion:
An atom or molecule with an electric charge due to the loss or gain of electrons.
Ionic compound:
Chemical compound formed of ions, held together by strong electrostatic forces.
Intermolecular forces:
The forces which exist between molecules. The strength of the intermolecular forces impact physical properties like boiling/melting point.
Lattice:
A repeating regular arrangement of atoms/ions/molecules. This arrangement occurs in crystal structures.
Liquid:
The state of matter where the particles are arranged randomly and close together and are able to move past each other.
Metallic bond:
The bonds present in metals between the positive metal ions and negatively charged electrons.
Metals:
Elements that react to form positive ions. Found to the left and towards the bottom of the periodic table.
Molecular formula:
The actual ratio of atoms of each element present in a compound.
Non-metals:
Elements that react to form negative ions. Found towards the right and top of the periodic table.
Particle theory:
The theory which models the three states of matter by representing the particles as small solid spheres. Particle theory can help to explain melting, boiling, freezing and condensing.
Polymers:
Large long-chain molecules made up of lots of small monomers joined together by covalent bonds.
Repeat unit:
The part of a polymer whose repetition would produce the complete polymer chain.
Solid:
The state of matter where the particles hold a regular arrangement and have the least amount of energy.
State symbols:
The symbols used in chemical equations to denote the states of the chemicals reacting:
(s) - solid
(l) - liquid
(g) - gas
(aq) - aqueous solution.
