C2 structure,bonding and the properties of matter Flashcards
Ionic bonding
Metals and non metals
Partials are oppositely charged ions
Structure- large crystals made from ions attracted to each other by electrostatic attraction
Room temp- solids
Melting point- high
Conductor of electricity- not when solid, yes when molten
Covalent bonding
Compounds of non metals and in most non metallic elements
Atoms that share pairs of electrons
Structure- molecules made from atoms bonded by covalent bonds
Room temp- liquid and gases
Melting point- low
Conductor of electricity- no or very little
Very strong
Metallic bonding
Metallic elements and alloys
Atoms that share delecoalised electrons
Structure- lumps or sheets of metal made from atoms packed together so that the delocalised electrons move through the fixed position
Room temp- solids (expect Mercury liquid)
Melting point- high
Sharing delocalised electrons makes strong bonds
Conductor of electricity- yes, good conductor
When metals and non metals transfer electrons
Atoms become charged. Make ions. Metal is positively charged Non metal is negatively charged Ionic bonding Positive and negative attracted by electrostatic attraction
Why do atoms bond
To make stable electronic structures
It is easier for metals to lose electrons and become positive ions
And easier for non metals to gain electrons to become negative ions
Giant structures
An ionic compound is a giant structure of ions in a lattice
Ball and stick diagram pros
The structure in 3D
The charges on the ions
The arrangement of ions in 3D
The type of ions in all directions
Ball and stick cons
Ions are actually closer together
Gives false image of bond direction when it is only electrostatic attraction
Ball and stick best represents
The number and type of ions in 3D
Close packed pros
The structure in 3D The charges on the ions The arrangement of ions In 2D (look at the front face of the diagram) The closeness of ions
Close packed cons
Difficult to see arrangement of ions in 3D
Close packed best represents
The way that ions are packed close together
States of matter
Solid} sublimation} gas Gas} condensation} liquid Liquid} boiling} gas Liquid} freezing} solid Solid} melting} liquid
In melting and boiling
Forces between particles decrease
Distance between particles increases
Arrangement becomes more random
Particles move more so need more energy from surroundings
In freezing and condensing
The strength of the particles remains the same
Distance between particles decreases
Arrangement becomes less random
Particles move less so less energy required from surroundings
Limitations of simple model
There are no forces represented between spheres
All particles represented as spheres
The spheres are represented as solid and inelastic
Small molecule
2 or 3 atoms joined together with no charge
Relatively low melting points and boiling points
Weak intermolecular forces
Can’t conduct electricity as have no charge
Polymers
Very large molecules
Atoms are linked to other atoms by strong covalent bonds
Form long chains
Intermolecular forces between polymer molecules are weaker
Allow chains to slide over each other but not pulled apart
Intramolecular bonds
The atoms of the monomers along the chains in a polymer are held together by strong covalent bonds. These are bonds within the polymer molecules
Intermolecular
The chains of the polymer are held together by weak forces of attraction. These forces between polymer molecules
Weak intermolecular forces of attraction
Stretches easily
Lower melting point
Strong cross linkes- chemical bonds between the chains
Rigid
Higher melting points
Making polymers
By addition
By condensation
Addition polymers
Long chains of units made from one molecule that has at least 1 double bond between carbon atoms
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Condensation polymers
Made of units using at least 2 different molecules
Losing a water molecule in the process
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Giant covalent structures
All atoms are linked to each other by strong covalent bonds
Eg. Diamond,silicon dioxide
Diamond properties
Lustrous Transparent Colourless Very hard Very high melting point Insoluble in water Doesn't conduct electricity
Silicon dioxide
White crystalline solid Very hard Very high melting point Insoluble in water Does not conduct electricity
Forms of carbon
Diamond
Graphite
Structures are very different
Structure of diamonds
Each carbon atom forms 4 bonds
Forms tetrahedron shape
The 4 covalent bonds makes it very hard to break
Carbon atoms share electrons
Graphite
Made from carbon
Carbon atoms only make 3 covalent bonds
Make hexagonal rings which form layers
Cut across layers but not through layers
No covalent bonds between layers
High melting point
Weak forces hold layers together
Sea of delocalised electrons conducts electricity
Delocalised electrons move easily along layers
Uses of graphite
Electrodes - conducts electricity
Lubricant- layers slide over each other
High temp lubricant- high melting point
Graphene
Single layer of graphite
One atom thick
Hexagonal rings of carbon atoms connected with strong covalent bonds
Fullerenes
Carbon rings can form hollow 3D shapes
Buckminsterfullerene
Bucky ball
Rings of 5&6 carbon atoms
C60
Spherical shape
Used in medicine
Uses of fullerenes
Drug delivery into the body Lubricants Catalysts Act as hollow cages to trap other molecules Make nanotubes
Nanotube properties
High tensile strength
High electrical conductors
High thermal conductivity
Nanotube uses
Semi conductors in electrical circuits
As catalysts
Reinforcing materials eg. Tennis rackets
Properties of graphene
2D compound Thermally stable Monolayer Electrical conductor through 'ballistic transport' Strongest material ever Elastic Absorb white light
Nanoparticals
Between 1&100 nm in size
Most are made from metals,metal oxides and silicates
Each nanoparticle contains only a few hundred atoms
When materials are present in nano particles it changes properties
Silver- stops bacteria growing (in clothes/deodorants)
Titanium dioxide- protects from ultraviolet light (in sun cream) bigger particles do the same but leave white coating on skin
Used to deliver drugs to the right cells
Nanoparticle safety
Avoid breathing in as can be hazardous
Could damage organs and tissue
Changing surface area to volume ratio
Nanoparticles
When a material becomes a nanoparticle its properties change
Gold- displays different colours
Titanium dioxide- becomes invisible
Silver- destroys bacteria
Other materials become more reactive as sa to v ratio increases making them better catalysts
Radius of atom
1 x 10-12 m
Radius of nucleus
1 x10-15 m
