C2 Structure and Bonding
- Created by: Hollie Wickens
- Created on: 17-09-13 20:15
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- Structures and Bonding
- Ionic Bonding
- Happens between a metal and non-metal
- The metal atoms lose electrons and become positive ions
- Involves the transfer of electrons to make ions
- The oppositely charged ions have a strong electrostatic force of attraction between them
- The non-metal atoms gain electrons and become negative ions
- The metal atoms lose electrons and become positive ions
- Involves the transfer of electrons to make ions
- The oppositely charged ions have a strong electrostatic force of attraction between them
- Giant Ionic Lattices
- In an ionic compound, millions and millions of ions are packed together in a regular lattice arrangement, joined by strong ionic bonds between oppositely-charged ions. This forms a giant 3D structure called an ionic lattice
- Properties of ionic compounds
- Most ionic compounds are soluble in water
- All ionic compounds have high melting and boiling points
- This is because in ionic compunds, the millions of ions form a giant ionic lattice, with the ions joined by strong ionic bonds
- Therefore it requires a lot of energy to weaken the millions of bonds in an ionic compund
- This is because in ionic compunds, the millions of ions form a giant ionic lattice, with the ions joined by strong ionic bonds
- Ions are electrically charged particles
- An electric current is the flow of electrically charged particles
- As a solid, the ions are vibrating in fixed positions and cannot move around
- When the ionic compound is melted, the ions can move around and conduct electricity
- When they dissolve, the ions are free to move around in the solution
- Most ionic compounds are soluble in water
- This means that ionic compounds that are soluble in water also conduct electricity when dissolved
- When they dissolve, the ions are free to move around in the solution
- When the ionic compound is melted, the ions can move around and conduct electricity
- As a solid, the ions are vibrating in fixed positions and cannot move around
- An electric current is the flow of electrically charged particles
- Happens between a metal and non-metal
- Covalent Bonding
- A covalent bond consists of a shared pair of electrons
- Covalent bonds are a result of electrostatic attraction between the positively-charged nuclei of the atoms and the negatively-charged shared electrons
- Simple molecular substances
- Low melting and boiling points
- Although the covalent bonds within these molecules are strong, the intermolecular forces between the molecules are weak and easy to break
- The intermolecular forces break when a substance melts or boils
- Although the covalent bonds within these molecules are strong, the intermolecular forces between the molecules are weak and easy to break
- Covalent molecules do not conduct electricity
- This is because their particles are not charged
- Unlike metals, covalent molecules do not have free electrons to conduct electricity
- This is because their particles are not charged
- Low melting and boiling points
- Giant covalent structures
- Diamond
- Very high melting and boiling points
- There are lots of strong covalent bonds that have to be broken
- Each carbon atom forms 4 covalent bonds
- Very hard, as all of the atoms are bonded together in a rigid network
- Doesn't conduct heat or electricity as there are no delocalised electrons
- Very high melting and boiling points
- Graphite
- Each carbon atom forms 3 covalent bonds
- Very high melting and boilng points
- There are lots of strong covalent bonds that have to be broken
- Soft and slippery, as the layers of atoms can slide over each other
- Conducts heat and electricity, as there are some delocalised electrons
- Diamond
- A covalent bond consists of a shared pair of electrons
- Metallic Structures
- Metals are giant structures of atoms
- The atoms in a pure metal are in tightly-packed layers, which form a regular lattice structure
- The outer electrons of the metal atoms separate from the atom, becoming delocalised
- These electrons are free to move through the structure
- The metal atoms become positvely charged ions and are attracted to the delocalised electroms because of the elecrostatic force of attraction
- This strong attraction is called metallic bonding
- Properties
- High melting points
- This property is due to the strong attraction betwen the positively-charged metal ions and thhe sea of delocalised electrons
- It takes a lot of energy to break down this very strong force of attraction
- This property is due to the strong attraction betwen the positively-charged metal ions and thhe sea of delocalised electrons
- Malleable + Strong
- When a metal is hit, the layers of metal ions are able to slide over each other, and so the structure doesn't shatter
- The metallic bonds don't break because the delocalised electrons are free to move throughout the structure
- When a metal is hit, the layers of metal ions are able to slide over each other, and so the structure doesn't shatter
- Conduction
- When a metal is heated, the delocalised electrons gain kinetic energy
- These electrons then move faster and so transfer the gained energy throughout the metal
- This makes heat transfer in metals very efficient
- Delocalised electrons also conduct electricity through metals in a simliar way
- This makes heat transfer in metals very efficient
- These electrons then move faster and so transfer the gained energy throughout the metal
- When a metal is heated, the delocalised electrons gain kinetic energy
- High melting points
- Polymers
- Thermosetting
- Thermosetting polymers harden on heating, and are harder to recycle
- They have more side chains and links to other chains
- It is very hard for the chains to move at all, so it cannot melt
- Once moulded, they do not soften when heated and they cannot be reshaped. Vulcanised rubber is a thermoset used to make tyres. Its polymer chains are joined together by cross-links, so they cannot slide past each other easily.
- Thermosoftening
- Thermosoftening polymers soften on heating and are easy to recylcle
- They're a tangle of smooth chains, and it's easy for the molecules to slide past each other and melt
- They can be shaped when hot. The shape will harden when it is cooled, but can be reshaped when heated up again. Poly(ethene) is a thermosoftening polymer. Its tangled polymer chains can uncoil and slide past each other, making it a flexible material.
- A polymer's use depends on both the monomer and the process used to make it
- High density polyethene (HDPE) is used for plastic bottles and water pipes
- HDPE and LDPE are made from the same monomer, but by different catalysts, temperatures and pressures, making different polyethenes with different properties
- Low density polyethene (LDPE) is used to make film and plastic bags
- HDPE and LDPE are made from the same monomer, but by different catalysts, temperatures and pressures, making different polyethenes with different properties
- Low density polyethene (LDPE) is used to make film and plastic bags
- High density polyethene (HDPE) is used for plastic bottles and water pipes
- Polymer molecules are long covalent chains made from carbon atoms, with various side groups attached
- Intermolecular forces between molecules are weak, but because the molecules are so large, the effect is greater, giving them higher melting points than expected
- Thermosetting
- Ionic Bonding
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