C2 Bonding,Structure,Properties of Matter

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Keisha M

Cards (25)

4.2.1.1 - Chemical bonds 
There are three types of strong chemical bonds: ionic, covalent and metallic.
For ionic bonding the particles are oppositely charged ions.
For covalent bonding the particles are atoms which share pairs of electrons.
For metallic bonding the particles are atoms which share delocalised electrons
4.2.1.2 - Ionic Bonding 
Ionic bonding is the transfer of electrons
When a metal and non metal react, the metal atom loses electrons to form a positively charged ion and the non metal gains these electrons to form a negatively charged ion
The oppositely charge ions are strongly attracted to one another by electrostatic forces making the ionic bond hard to break
Dot and cross diagrams show how ionic compounds are formed
Electrons get transferred to form a full outer shell
Ionic bonding dot and cross diagram
4.2.1.3 - Ionic Compounds
An ionic compound is a giant structure of ions held together by strong electrostatic forces of attraction between oppositely charged ions
These forces act in all directions in the regular lattice arrangement they're in
Ionic compounds have high melting and boiling points due to the large amounts of energy needed to break the many strong electrostatic forces
Ionic compounds can conduct electricity when melted or dissolved in water because the ions are free to move around so charge can flow
The greater number of charges the stronger the ionic bonds
Empirical Formula of ionic compounds
the simplest whole number ratio of atoms of each element in a molecule
The molecular formula tells you the actual number of atoms of each element in a molecule while empirical formula is the ratio
e.g. the molecular formula of hexane is C6H14 find the empirical
divide the number of atoms for each element by a common factor in this case they can both be divided by 2
Empirical formula = C3H7
if given a dot and cross diagram just count up the number of ions of each element there are
4.2.1.4 - Covalent Bonding 
Covalent bonding is the sharing of electrons
A covalent bond occurs when non metal atoms share pairs of electrons in their outer shell
The positively charged nuclei of the bonded are attracted to the shared pair of electrons by electrostatic forces creating strong covalent bonds
A single covalent bond provides one extra electron
Many elements are simple molecules; two or more atoms joined by a covalent bond e.g. polymers have very large molecules
Simple covalent molecules have relatively low melting and boiling points
How to draw a covalent bond 
Dot and cross diagrams with the electrons drawn in the overlap between outer shells
Displayed formula shows covalent bonds as single lines between atoms
3D model
Three ways to draw covalent bonds:
4.2.1.5 - Metallic bonding 
Metallic bonding involves delocalised electrons
Metals consist of giant structures of atoms arranged in a regular pattern with delocalised electrons in-between layers
The electrons in the outer shell of metal atoms are delocalised (free to move around)
The positive metal ions have an electrostatic attraction with the sea of delocalised electrons
The electrostatic forces between the metal atoms and delocalised electrons are very strong so need lots of energy to break causing metals to be solid at room temperature and have high melting and boiling points
Alloys 
Alloys are made by combining two or more metals or a metal and another metal to enhance certain properties such as strength, durability and corrosion resistance e.g. Steel is made from iron and carbon
Alloys are harder than pure metals because the new atoms will distort the layers of metals making it more difficult for them to slide over each other whereas pure metals are malleable due to layers being able to slide over each other so they are liquid or soft
4.2.2.1 - The three states of matter 
The three states of matter are solid, liquid and gas.
Melting and freezing take place at the melting point
Boiling and condensing take place at the boiling point.
The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance
The stronger the forces between the particles the higher the melting point and boiling point of the substance
Limitations of the simple particle model is there are no forces and all particles are represented as solid spheres
4.2.2.4 - Properties of small molecules 
Substances with small molecules are usually gases or liquids that have relatively low melting and boiling points
They have weak intermolecular forces which increase with the size of the molecules so larger molecules have higher melting and boiling points
They do not conduct electricity since the molecules don't have an overall electric chatge
When substances melt or boil its the intermolecular forces which are overcome not the covalent bonds
4.2.2.5 - Polymers 
Polymers have very large molecules and the atoms in the polymer molecules are linked to other atoms by strong covalent bonds
The intermolecular forces between polymer molecules are relatively strong so they are solid at room temperature but their boiling points are still lower than ionic or giant molecular compounds
4.2.2.6 - Giant Covalent Structures 
Substances that consist of giant covalent structures are solids with very high melting points.
All of the atoms in these structures are linked to other atoms by strong covalent bonds.
These bonds must be overcome to melt or boil these substances.
Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures.
4.2.2.7 - Properties of Metals and Alloys 
Pure metals are too soft for many uses since their atoms are arranged in layers which can slide over each other so they are mixed with other elements to make alloys which are harder due to the distorted layers
Metals are good conductors of electricity since the delocalised electrons carry an electrical charge through the metal
Metals are good conductors of heat because energy is transferred by the delocalised electrons
Metals have high melting and boiling points due to strong electrostatic forces
4.2.3.1 - Diamond 
Diamond is an allotrope of carbon and has a giant covalent structure made up of carbon atoms which form four covalent bonds
The strong covalent bonds need lots of energy to break making diamond hard and giving it a very high melting and boiling point
Does not conduct electricity since there are no free electrons or ions to carry charge
low chemical reactivity
4.2.3.2 - Graphite 
Graphite is an allotrope of carbon with a giant covalent structure with each carbon atom forming three covalent bonds formed in hexagons giving it a high melting point since the covalent bonds need lots of energy to break
No covalent bonds between layers so they are free to slide over each other making graphite soft, slippery and a good lubricating material
Only 3 out of carbons 4 outer electrons are used in bonds so each carbon atom has one delocalised electron which conducts electricity in graphite
4.2.3.3 - Graphene 
Graphene is a single layer of graphite
Graphene is a sheet of carbon atoms joined together in hexagons and because the sheet is one atom thick it is a two dimensional substance
The network of covalent bonds makes graphene very strong and light so it can be added to composite materials to improve their strength
Can conduct electricity from it's delocalised electrons
4.2.3.3 - Fullerenes 
Fullerenes are molecules of carbon atoms with hollow shapes.
The structure of fullerenes is based on hexagonal rings of carbon atoms but they can also be arranged in pentagons or heptagons due to having 5 or 7 carbon atoms
The first fullerene to be discovered was Buckminsterfullerene (C60 ) which has a spherical shape.
Can be used to cage other molecules or deliver a drug into the body
Have a large surface area so make good catalysts or lubricants
Nanotubes 
Carbon nanotubes are cylindrical fullerenes
Have very high length to diameter ratios which make them useful for nanotechnology, electronics and other materials
Have high tensile strength meaning they can stretch
4.2.4.1 - Nanoparticles 
Nanoparticles are extremely tiny and are put in categories based on their diameter
Coarse particles (PM10) are airbone particles like dust with diameters between 2.5um and 10um
Fine particles have a diameter of 01.um - 2.5um
Nanoparticles contain only a few hundred atoms and are invisible in light. They are 100 times smaller than the finest particles
Nanoparticles have a large surface area to volume ratio creating faster chemical reactions
Uses of nanoparticles 
Effective because smaller quantities are needed to produce the same effect as standard amounts sine their high surface area to volume ratio means a greater proportion of particles are exposed
Nanoparticles have applications in medicine, electronics, cosmetics, deodorants, sun creams, clothes and catalysts
In sun cream nanoparticles of titanium oxide are used as they make it easier to rub in and make it more transparent
Nanoparticles are dangerous since they are explosive
Solids, Liquids and gases
Solids have strong forces of attraction between particles and keep a definitive shape and volume. Particles vibrate in a fixed position
Liquids have weak forces of attraction between particles and are randomly scattered and free to move past each other. Liquids expand slightly when heated
In gases the forces of attraction are very weak and are free to move far apart. Gases expand when heated
Formation of Ions 
Ions are made when electrons are transferred through atoms losing or gaining them when they want to get a full outer shell
Atoms with full outer shells are very stable (noble gases)
The number of electrons lost or gained is the same as the charge on the ion e.g. if an atom loses 2 electrons the charge is 2+
Positive ions = cations
Negative ions = anions
Ionic bonding = metal + non metal
Covalent = non metal + non metal
Metallic = metal + metal/alloys