Bonding Flashcards
What does ionic bonding occur in?
- metals and non-metals
Describe ionic bonding
- metal ion loses electrons to form a full outer shell
- becomes positve (state charge here) ion
- non-metal ion gains electrons, forms full outer shell
- becomes negative (insert charge) ion
- strong electrostatic forces of attraction between opposite charges bond them together
Describe the structure of an ionic compound
- giant ionic lattices
- regular structure
- strong electrostatic forces of attraction between oppositely charged ions
- forces act in all directions
What are the properties of ionic compounds?
- high melting and boiling point : the lattice structure and the strong electrostatic forces between the ions require a lot of thermal energy to break
- Crystalline : this reflects the regular arrangement of teh ions
- brittle : small distortions in the crystal bring ions with the same charge together and similar charges repel each other, breaking the crystal apart
- soluble in water : the slightly negative oxygen in the water attracts the positive ions while the slightly oxygen hydrogen in the water attracts negative ions, pulling the crystal apart
- do not conduct when solid : the ions cannot move when the ionic compound is solid there cannot carry any charge and cannot conduct electricity
- conduct when molten/ in solution : the ions are free to move when molten or dissolved and will carry the charge and conduct electricity
What does covalent bonding occur in?
- between non metals
Describe covalent bonding
- pairs of electrons shared between atoms
- gives full outer shells
What are the three types of molecule that can be formed by covalently bonded substances?
- small molecules
- very large molecules
- giant covalent structures
What are the properties of small molecules?
- low melting and boiling points
- usually gases or liquids at room temp
- weak intermolecular forces (much weaker than covalent bonds)
- larger molecules = stronger intermolecular forces = higher boiling/ melting points
- do not conduct electricity (no electric charge)
What are the properties of very large molecules?
- high melting and boiling points
- solids at room temp.
- strong intermolecular forces between polymer molecules
What are large molecules?
- polymers made by joining many monomers together
- atoms in polymer molecules linked to other atoms by strong covalent monds
polymers have very large molecules
What are the properties of giant covalent structures?
- solids with very high melting points
- all atoms linked to other atoms by strong covalent bonds
- these bonds must be overcome to melt or boil these substances
What are the properties of graphite?
- high melting point
- conducts electricity
- slippery (weak intermolecular forces, layers slide over each other)
Describe graphite
- each carbon has 3 covalent bonds to other carbon atoms
- weak intermolecular forces between layers
- layers can slide over each other
- one delocalised electron per atom
Describe diamond
- each carbon atom covalently bonded to 4 other carbon atoms
- no delocalised electrons
What are the properties of diamond?
- very hard
- high melting point (high energy breaking covalent bonds)
- doesn’t conduct electricity)
Describe graphene and its properties
- single layer of graphite
- conducts electricity (delocalised electrons) used for electronics
- strong covalent bonds used for composites
Describe metallic bonding
- electrostatic force of attraction between positively charged centres of metal atoms and delocalised electrons
- electrons can move through structure
- metals = giant structures of atoms arranged in a regular pattern
What are the properties of metals?
- high melting and boiling points (giant structure of strong metallic bonding)
- can be bent or shaped- pure metals = atoms arranged in layers, can slide over each other
- good electrical conductors - delocalised electrons carry electrical charge through structure of metal
- good thermal conductors - energy transferred by delocalised electrons
What are the properties of alloys?
- harder than pure metals- distorted layer structure
- harder to slide over each other
What are fullerenes?
- molecules of carbon atoms with hollow shapes
- based on rings of carbon atoms (5-7)
What is C60?
- spherical shape
- buckminsterfullerene
What are nano tubes?
- cylindrical fullerenes
- high length to diameter ratio
What are fullerenes used for?
- nanotechnology
- electronics
- lubricants (particles can roll)
How large are nanoparticles?
1-100nm
a few hundred atoms
How big are fine particles?
PM2.5
diameter 100-2500nm
How big are coarse particles?
dust
PM 10
10 000 nm
What is the rule of SA to volume ratio?
- side decreases by factor of 10
- SA to volume ratio increases by fator of 19
Why do nanoparticles have different properties from the same materials in bulk?
- because of their high surface area to volume ratio
- smaller quantities needed to be effective than normal particle size
What are the risks of using nanoparticles?
- can enter human body (breathing, cuts, ingested)
- might carry toxic substances into cells
- catalyse damaging reactions
unsure of long term effects
What are nanoparticles used for?
- electronics (high length to diameter ratio, smaller components)
- cosmetics (small size = absorbed into skin better, absorbs UV light)
- deodorants (high SA to volume ratio)
- medicines (small size penetrates cell walls, high length to diameter ratio)
- catalysts (high SA to volume ratio)
What are the disadvantages of using a ball and stick model?
- doesn’t show electrons
- appears large gaps between atoms
What are the disadvantages of using dot and cross diagrams?
- 2D
- don’t show bond angles
