Topic 2- Bonding, Structure and the Properties of Matter Flashcards
What is ionic bonding?
Ionic bonding is the electrostatic attraction between positive and negative ions (oppositely charged)
It is a relatively strong attraction
metals combined with non metals
How are ionic compounds held together?
They are held together in a giant lattice
It is a regular 3D structure that extends in all directions in a substance
Electrostatic attraction between positive and negative ions holds the structure together
What does ionic bonding consist of?
Its when electrons in the outer shell of the metal atom are transferred
Metal atoms lose electrons to become positively charged ions
Non-metal atoms gain electrons to become negatively charged ions
State properties of ionic substances
High melting and boiling points (due to strong electrostatic forces between oppositely charged ions)
Do not conduct electricity when solid (ions in fixed positions)
Conduct electricity only when molten or dissolved in water (ions are free to move)
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 and 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?
They are large covalently bonded molecules
Intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature
What are giant covalent substances?
Solids, atoms covalently bonded together in a giant lattice
High melting/boiling points - strong covalent bonds
Mostly don’t conduct electricity (no delocalised electrons)
Diamond, graphite, silicon dioxide
Describe and explain the properties of diamond
Four, strong covalent bonds for each atom.
It is very hard (due to strong bonds)
Very high melting point (due to strong bonds)
Does not conduct electricity (no delocalised electrons)
Describe and explain the properties of graphite
Three covalent bonds for each carbon atom
Layers of hexagonal rings
High melting point
Layers free to slide due to weak intermolecular forces and no covalent bonds between layers
Soft, can be used as a lubricant
Conducts thermal and electricity due to one delocalised electron per carbon atom
Describe and explain the properties of fullerenes
Hollow shaped molecules
Based on hexagonal rings but can also contain rings with five or seven carbon atoms
Describe and explain the properties of nanotubes
They are cyclindrical fullerenes with very high length to diameter ratios
High tensile strength (strong bonds)
Conductivity (deloc. electrons)
Describe and explain the properties of graphene
Single layer of graphite
Has properties that make is useful in electronics and composites
Graphene is very strong because atoms within its layers are very tightly bonded
It is also elastic because the planed of atoms can flex relatively easily without the atoms breaking apart
What are some of the uses of graphene and fullerenes?
They can be used as lubricants, to deliver drugs in the body and catalysts
Nanotubes can be used for reinforcing materials, for example tennis rackets
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 (deloc. electrons)
Malleable, soft (layers of atoms can slide over each other whilst maintaining the attraction forces)
What are alloys and why are they harder than pure metals?
Mixtures of metal with other elements which are usually metals
Different sizes of atoms distorts the layers, so they can’t slide over each other meaning they are harder than pure metals
What are fine and coarse particles?
Fine particles (soot), 100-2500 nm diameter
Coarse particles (dust) 2500-1,000,000 nm diameter
Explain why graphite is soft and is a good conductor of electricity
Each atoms forms 3 covalent bonds
This forms layers
Layers can slide over each other
Delocalised electrons
Why do carbon nanotubes conduct electricity?
They contain delocalised electrons
Electrons can move through the structure
Give one limitation of using a dot and cross diagram to represent a molecule
It is two dimensional
Why does ammonia have a low boiling point?
Small molecules
Weak intermolecular forces
Less energy needed to break down
A student added copper metal to colourless silver nitrate solution
The student observed:
- pale grey crystals forming
- the solution turning blue
Explain how these observations show that silver is less reactive than copper
The crystals are silver
The copper ions are blue
This is because copper displaces silver
