topic 7- structures (inc ionic, giant covalent, simple covalent, polymers and metals) Flashcards
Features of giant covalent structures
- high melting point
- no specific formula
- 1 large molecule
Ball and stick diagrams
(i) this component represents bonds between atoms
(ii) this component represents atoms
(i) stick
(ii) ball
Why do giant covalent structure ps have very high melting points?
As they have very strong covalent bonds between the atoms
Why is diamond hard?
It has lots of strong covalent bonds
Why doesn’t diamond conduct electricity?
It has no delocalised electrons in its structure
Why does diamond have a high melting point?
A lot of energy is needed to break the strong covalent bonds. Therefore it has a high melting point
In diamond, each carbon atom is bonded to __ other carbon atoms by strong covalent bonds
4
What is carbon?
A giant covalent structure
What shape are the carbon atoms in graphite’s layers?
Hexagonal (6-sided)
Graphite has ____ intermolecular forces keeping layers together
Weak
Why is graphite very soft?
It’s layers can easily slide over one and another
In graphite, each carbon atom is bonded to __ other carbon atoms by strong covalent bonds
3
Why can graphite conduct electricity?
- each carbon atoms forms three bonds
- this means that there is a delocalised electron from every carbon atom
- this electron can move freely, therefore graphite is a good electrical conductor
What are fullerenes?
Molecules of carbon atoms that take up hollow structures. Their structure is usually carbon atoms arranged in hexagonal (6-sided) rings, but pentagonal (5-sided) and heptagonal (7-sided) carbon rings can also be found.
What type of molecule is buckminsterfullerene?
A simple molecule because of its fixed size
What shape is the buckminsterfullerene?
Spherical
What is the formula for buckminsterfullerene?
C60
Common uses of spherical fullerenes:
- catalysts
- lubricants
- as vehicles for transporting drugs into our bodies
Carbon nanotubes are…
Cylindrical fullerenes
Why are carbon nanotubes exceptionally strong for their size?
because of strong covalent bonds between carbon atoms
uses of cylindrical fullerenes:
- in electronics
- in nanotechnology
- for strengthening materials (e.g. tennis racket frames)
Carbon nanotubes are often called molecular wires, why?
As they have a tiny diameter but can be incredibly long
Why does graphene conduct electricity?
Graphene is a single layer of graphite so it also conducts electricity because of the carbon atoms’ delocalised electrons
Why is graphene light?
It has a thickness of just 1 atom. This means it’s almost a two dimensional structure and so graphene is very light
Why is graphene very strong?
It has strong covalent bonds between carbon atoms
What are graphene’s uses?
Graphene has lots of uses in electronics and composite materials
>graphene makes materials stronger without making them much heavier
>graphene can be used in solar panels, batteries and so much more
What are polymers?
Large chain-like molecules that can extend for thousands of atoms.
Polymers are held together by…
- weak intermolecular forces between molecules
- strong covalent bonds between atoms in molecules
What state are polymers usually at room temperature?
Solid
Why do the intermolecular forces in polymers add up to be quite strong?
Because of the large size of polymer molecules
Why do many polymers melt easily?
The intermolecular forces between molecules remain less strong than chemical bonds
What does the ‘n’ in the bottom right of a polymer diagram tell us?
How many times the unit is repeated to create the larger polymer molecule
When polymers undergo addition ____, poly(propene) is the product
-polymerisation
Why are pure metals soft and malleable?
Because the ions are arranged in layers, they easily move over each other when a force is applied
Why do pure metals have high melting and boiling points?
There are strong electrostatic forces between metal ions and delocalised electrons
What are metals made up of?
Giant structures of regularly arranged atoms
What is the structure of pure metals?
A regular lattice of positive ions, cations, in a ‘sea’ of delocalised electrons
Delocalised electrons are…
-not bound to an atom and are free to move around within the lattice
When does delocalisation happen?
When metal atoms have a small amount of electrons in their outer shells
Which would a metallic bonding be found in:
- sodium (Na)
- sodium chloride (NaCl)
-sodium (Na)
Why are metals good conductors of electricity and heat?
Because their delocalised electrons can carry a charge/ heat throughout the structure. The electrons move from the negative terminal to the positive terminal
Which bonds have 2 atoms sharing 1 or more pairs of electrons and are found in most non-metal compounds?
Covalent
Which bonds involve an attraction between positive ions and negative, delocalised electrons
Metallic
What is an ionic bond formed from?
An attraction between a negatively charged ion (anion) and a positively charged ion (cation)
What forces hold together an ionic lattice?
Electrostatic forces
What is the empirical formula of C7H4O2?
C7H4O2
What type of bonding involves the movement of electrons from one atom to another?
Ionic
What is happening during freezing?
Molecules are losing energy, moving around less and forming a fixed lattice
Which of these is a property of ionic compounds:
(i) can conduct electricity while solid
(ii) cannot conduct electricity when molten
(iii) have high melting points
(iii) have high melting points
which molecule has a higher boiling point:
(i) chlorine
(ii) sucrose
(ii) sucrose
Which of the following can conduct electricity?
- NaCl(aq)
- diamond
- polythene
- graphite
-NaCl(aq) and Graphite
What is the charge on a carbonate ion?
2-
How many double bonds and single bonds are there in a carbonate ion?
Number of single bonds= 2
Number of double bonds= 1
Why do electrons become delocalised in metals?
Because the electron orbitals in the metal atoms overlap
Displacement reactions
When a more reactive metal (one that forms positive ions more easily) can displace a less reactive metal from a compound
