What are the general properties of covalent and simple molecular compounds?
low melting and boiling points and do not conduct electricity
what do all compounds have in common?
they all consist of atoms of more than one element which are chemically joined together by bonds
what is a compound?
A compound is a substance made up of two or more different elements chemically bonded together.
what is a simple molecular covalent structure?
a compound that exist as a molecules which are groups of atoms joined together by covalent bonds
what are the intermolecular forces between molecules like?
although they have strong covalent bonds the forces of attraction or intermolecular forces are weak
why cant simple molecule conduct electricity?
the molecules have no overall charge and the electrons can’t flow because the shared electrons are held in place between two bonding atoms with strong forces of attraction because of a positively charged nuclei
why do molecules have a low melting point?
because of the low intermolecular forces
what is a polymer?
A long chain molecule made by joining together many monomers
what is a monomer?
a simple small molecule that can join together with each other in a chain to form a polymer
what are some properties of a longer polymer?
they have higher intermolecular forces and higher melting and boiling points than shorter ones and sometimes get tangled up with one another.
What are some allotropes of carbon?
Diamond, graphite, graphene, fullerenes
What is the structure of diamond?
Giant covalent structure, tetrahedral arrangement
what is the structure of graphite?
giant covalent structure
what is the structure of fullerenes?
simple molecule, covalently bonded to 3 other carbon atoms, tubular or spherical molecules
what is the structure of graphene?
1 atom thick, light material, sheet of carbon atoms, no fixed formula
what are the properties of diamond?
very hard, strong covalent bonds, high mp, does not conduct electricity and a good insulator
what are the properties of graphite?
delocalised electron, high mp, conduct electricity
what are the properties of fullerenes?
low mp, ball, soft and slippery
what are the properties of graphene?
Good electrical conductor, con be a sheet or a tube
How are particles arranged in metals?
All they same size, packed closely together in layers to form s giant metallic lattice
what is metallic bonding?
the electrostatic attraction between positive metal ions and the negative delocalised electrons, the attraction is very strong so metals have high melting and boiling points.
why are metals malleable?
the ‘sea’ of delocalised electrons still hold the ions together so the metal changes shape instead of breaking.
why do metals conduct electricity?
the delocalised electrons can move freely so when voltage is applied to two points of the metal the electrons flow towards the positive side, the transfer of energy forms an electric current
what are typical properties of metals?
Lustrous, malleable, ductile, good conductors of heat and electricity
what are the typical properties of non metals?
Non-lustrous, brittle, poor conductors of heat and electricity
what are the limitations of dot and cross diagrams?
does not show the shape of the molecule accurately, can make it look like electrons from different atoms are different, does not show size of atoms
what are the advantages of dot and cross diagrams?
shows what happens to the electrons when bonds are formed, explains how the formula of compounds is obtained
what are the limitations of displayed formulas diagrams?
Does not show how bonds are formed, does not show the shape of the molecule, does not show the relative sizes of the atoms
what are the advantages of dot and cross diagrams?
shows the number if atoms of each element in a molecule, shows the formula of elements of compounds
what are the limitations of 3D space filling model?
Does not explain how bonds are formed, does not show the electrons
what are the advantages of 3D space filling diagrams?
shows the shape of molecules and shows the relative sizes of atoms