C3 Structure and Bonding Flashcards
What are the 3 states of matter?
Solid, Liquid and Gas
How are solid particles arranged?
- Tightly packed
- Arranged in rows
- Vibrate in fixed positions
- Fixed shape and volume
- Low kinetic energy
- Cannot be compressed
How are liquid particles arranged?
- Close together
- Irregular pattern
- Can slide past each other
- Shape can change
- Fixed volume
- Medium kinetic energy
- Cannot be compressed
How are gas particles arranged?
- Widely spaced
- Arranged randomly
- Move freely in all directions
- Change shape and volume
- Most kinetic energy
- Can be compressed
What are all the change in states?
Melting - Solid to liquid
Freezing - Liquid to solid
Evaporate - Liquid to gas
Condensing - Gas to liquid
Sublimation - Solid to gas
Deposition - Gas to solid
What happens to bonds during a change of state?
Bonds are either being broken or being made. Thermal energy added is used to break existing bonds between the molecules within the substance while thermal energy lost is replaced as new bonds form
Breaking bonds - Endothermic
Making bonds - Exothermic
Why do atoms form bonds?
Each shell has a maximum number f electrons that it can hold. Electrons fill the shells nearest the nucleus first
What are the types of bonds?
Ionic - between metal and non-metal
Covalent - between non-metals
Metallic - between metals
What are ions?
A charged particle formed when an atom gains or loses electrons.
Why can ions not be neutral?
Atoms are neutral because the number of protons = electrons and neutrons have a neutral charge. When the atom gains or loses an electron to become an ion, the number of protons and electrons won’t be balanced, therefore they will not cancel each other out.
What is a half equation?
Show each separate process in terms of electron movement. E.g. (Al3+) + (3e-) → Al. Aluminium ion gains three electrons to become an aluminium atom
What is ionic bonding?
- Occurs when oppositely charged ions attract and bond together
- Happens between metals and non-metals
- Held in a giant lattice by strong electrostatic forces
What is the empirical formula?
Simplest whole number ratio of atoms present in a compound. E.g. Glucose formula is C6H12O6 -> 6 carbon, 12 hydrogen, and 6 oxygen atom. The empirical formula of glucose is CH2O (everything divided by 6)
What is the structure of ionic compounds?
- Strong electrostatic forces between positively and negatively charged ions - hard
- This forms a lattice -> regular, ordered structure of repeating units
- All ionic compounds form lattices and crystals when solid
Why are ionic compounds brittle?
- Layer of ions is shifted when the lattice is hit so that ions with the same charges are lined up
- These repel each other and so split the ionic lattice causing it to shatter
Why do ionic compounds have high melting and boiling points?
Ionic compounds form giant lattices (repeated structure)
- There are strong electrostatic forces between oppositely charged ions
- Lots of energy is needed to overcome these forces
Why do some ionic compounds form solutions with water?
The water molecules will break up the lattice into ions (Giant ionic compounds will dissolve)
Why can ionic compounds conduct electricity when in solution or molten, but not when they are solid?
- Solids do not have free ions
- Molten can conduct electricity -> ions are free to move around and conduct
What is a covalent bond?
- Two non-metal atoms cannot form a bond by transferring electrons from one to another.
- Instead, they share electrons.
- Shared electrons join the atoms together.
Forces between simple covalent molecules?
Attractive forces between these molecules keep them in proximity to one another. They have weak intermolecular forces.
What are intermolecular forces?
The force of attraction between neighbouring molecules. Intermolecular forces increase with the size of the molecules
What does a strong intermolecular force mean?
The molecules have high melting and boiling points. More energy is required to break the force.
What are the properties of Simple Covalent Molecules?
- Intermolecular forces are weak
- Little energy is needed to break them
- Low melting and boiling points
- (Mostly) gases at room temperature
What are monomers?
they are small molecules that can be joined in a chain to form a much larger molecule called a polymer. Individual monomer units can be attached with a covalent bond
What is the intermolecular force in polymer chains?
Longer chains have stronger forces. The long chains can also become tangled together
What are giant covalent structures?
- Most notably carbon and silicon
- Sometimes called macromolecules
Properties of giant covalent structures
- Very hard and strong
- Very high boiling and melting point
- Insoluble in water
- Diamond in particular is a very strong
What is the structure of a diamond?
- Carbon atoms held together by covalent bonds
- 4 bonds per atom
- Maximum number of bonds formed
- All 4 outer electrons used up in covalent bonds
What are the properties of a diamond?
- Very hard
- No free electrons -> cannot conduct electricity
What is a graphene?
2D hexagonal sheets of carbon
What is graphite?
3D lattice consisting of multiple graphene layers
What is the structure of graphite?
- Hexagonal sheets of covalently bonded carbon atoms (graphene) arranged in layers
- 3D lattice
- 3 covalent bonds per atom
- Weak intermolecular forces acting between graphene layers
What are the properties of graphite?
- 3 bonds per atom
- 3 out of the 4 outer electrons are used up in covalent bonds
- 1 delocalised electron which allows it to conduct electricity
- Weak intermolecular forces between graphene layers
- Layers can slide over each other -> soft
What is a fullerene?
- Large but are not classified as giant structures
- Made by conjoined hexagonal carbon rings
- Buckminsterfullerene is one type. It contains 60 carbon atoms, each of which is bonded to 3 others with 3 covalent bonds
What are carbon nanotubes?
- Fullerenes which form incredibly thin cylinders, whose length is much greater than their diameter
What are the properties of carbon nanotubes?
- High tensile strength -> reinforcing composite materials
- High electrical and thermal conductivity
What are the uses of fullerenes?
- Drug delivery
- In lubricants
- As catalysts in reaction
- To make carbon nanotubes to reinforce structures
- Flexible electronic displays
what is the structure of metallic bonds?
- Giant structures
- Lattice of positive metal ions in regular layers
- Outer electrons can easily move
- Form a ‘sea’ of free electrons (delocalised electrons)
- Strong electrostatic attraction between positive ions and negative sea of electrons bond metal ions together
- Electrons act like flexible glue
Why does metal bend instead of breaking?
- Electrons do not belong to specific atoms, they are delocalised
- Metal atoms form positive ions
- Attraction between particles with opposite charges holds the metal together
- No specific bonds exist between adjacent atoms/ions
- Atoms/ions can slide over each other allowing metals to bend
What is galvanising?
Metallic compounds form crystals -> can be very small, however you can often see them. Metal crystals will easily form over other metals in galvanising
What is galvanising for?
To protect metals. E.g. Zinc is galvanised over steel to stop it from rusting
What is an alloy?
A mixture of 2 or more elements, at least one of which is a metal
why are alloys harder than pure metals?
- Different elements have different-sized ions
- Makes the structure less regular
- Layers of ions can’t slide over each other as easily -> makes the material harder
- Also makes the material more brittle because it is more likely to fracture (crack) and size
What are the properties of nanoparticles?
May have properties different from those for the same material in bulk because of their high surface area to volume ratio -> smaller quantities are needed to be effective than for materials with normal particle size
What is the surface area to volume ratio?
Huge proportion of their atoms at the surface of the particle -> give them huge SA:V
As the side of a cube decreases, the SA:V ratio increases in proportion
What are the uses of nanoparticles?
- Absorbing UV radiation -> Sunscreen
- Acting as catalysts (speed up reactions) -> Self-cleaning glass
- Healthcare -> fighting cancer, delivering drugs using nanocages, making drugs easier to absorb
- Electronics -> Smaller, more powerful computers and electronic devices
What are the problems when using nanoparticles?
- Might catalyse reactions -> effects we don’t want them to
- Easily absorbed into our bodies -> interfere with chemical reactions going inside
- Some nanostructures are similar shapes and sizes -> mix up
What is nanoscience
The study of small particles that are between 1 and 100 nanometres in size
