C2 - Bonding, Structure, & The Properties Of Matter Flashcards
(27 cards)
What is ionic bonding?
The electrostatic attraction between positive & negative ions.
It is a relatively strong attraction.
How are ionic compounds held together?
• Held together in a giant lattice
• A regular structure that extends in all directions in a substance
• Electrostatic attraction between positive & negative ions holds the structure together
State properties of ionic substances
• High melting & 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 & 5 examples of negative ions (give names of negative anions).
What is important when working out a formula of an ionic compound?
Positive: Na+, Mg2+, Al3+, Ca2+, Rb+
Negative: Cl-, Br-, So4(2-), No3-,OH- (Chloride, bromide, sulfate, nitrate, hydroxide)
• Ionic compounds are electrically neutral, I.e. positive & 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 in group 2, so 2 available outer electrons.
O is in group 6, so can accept 2 electrons to get full outer shell.
Mg becomes Mg2+ and O becomes O2- (oxide)
What is a covalent bond?
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 & boiling points
How do intermolecular forces change as the mass 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?
Polymers are very large molecules (>100s, 1000s of atoms) with atoms linked by covalent bonds
What are thermostoftening polymers?
Special type of polymers; they melt/soften when heated.
No bonds between polymer chains.
Weak intermolecular forces ensure that the structure is solid at room temp. These forces are overcome with heating - polymer melts.
What are giant covalent substances?
Give examples
- Solids, atoms covalently bonded together in a giant lattice.
- High melting/boiling points - strong covalent bonds.
- Mostly don’t conduct electricity (no delocalised e-).
- Diamond, graphite, silicon dioxide .
Describe & explain the properties of 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 of 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 & electricity due to one delocalised electron per each carbon atom
Describe & explain the properties of Fullerenes
- hollow shaped molecules
- based on hexagonal rings but may have 5/7-carbon rings
- C60 had spherical shape, simple molecular structure (Buckminsterfullerene)
Describe and explain the structure of Nanotubes
- Cylindrical fullerene with high length to diameter ratio
• High tensile strength (strong bonds)
• Conductivity (deloc. Electrons)
Describe & explain the structure of graphene
A single layer of graphite
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 & 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 alloys are harder than pure metals.
What are the limitations of the simple model
• There are no forces between spheres & atoms.
• Molecules & 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 & the structure of the substance.
The stronger the forces between the particles the higher the melting point & boiling point of the substance.
A pure substance will melt or boil at?
What about a mixture?
• A fixed temperature
• A mixture will melt over a range of temps
What are the 3 states of matter?
Solid, liquid & gas
What is nano science?
Science that studies particles that are 1-100nm in size
