What is meant by compound
substances in which atoms of two or
more elements are chemically combined.
Chemical bonding involves what
either transferring or sharing electrons in the highest occupied energy levels (shells) of atoms
Why are electrons shared or transferred in chemical bonding
So that the compound has the electronic structure of a noble gas ( full outer shell )
When atoms form chemical bonds by transferring electrons this is called a
ionic bond
Atoms that lose electrons become
positively charged ions
Atoms that gain electrons become
negatively charged ions
Ions should have the electronic structure of which periodic group
0 ( noble gases )
Elements from group 7 ( halogens ) react with which elements to form ionic compounds
All the alkali metals
An ionic compound can be described as what ( in the context of size )
giant structure
Ionic compounds are held together by what
Strong electrostatic forces of attraction between oppositely charged ions
Ionic compounds have what form
Lattice
When atoms form chemical bond by sharing electrons this is called
covalent bond
Are covalent bonds strong or weak
Strong
Metal molecules consist of what type of structure
Giant structures of atoms arranged in a regular pattern
Electrons is the highest energy level are…
delocalised
Delocalised means
Free to move through the whole structure
Substances that consist of simple molecules have relatively high or low melting and boiling points
low
Why do ionic compounds have high melting points
Lots of energy is required to break the many strong bonds
Why is it that when ionic compounds are melted they can conduct electricity
The ions are free to move and carry the current
Macromolecules, or giant structures can form from what
Atoms that share electrons ( covalent bonding )
How many covalent bonds of each carbon atom form diamond
4
What size is diamonds structure
massive
How many covalent bonds of each carbon carbon atom forms graphite
3
What is the structure of graphite and what is the nature of these layers
Layers which slide over each other
Why do the layers in graphite slide over each other
Because there are no covalent bonds between the layers meaning there is weak force causing this slipperiness
Why can graphite conduct heat and electricity
Because each atom has one delocalised electron
What can fullerenes be used for
drug delivery in the body, in lubricants and for catalysts
What can nanotubes be used for
reinforcing materials such as tennis rackets
Why can metals conduct electricity and heat
Because of the delocalised electrons in their structures
Why can metals be bent and shaped
Because the layers of atoms in metals are able to slide over each other
Alloys are made from what
two or more different metals
Why does making an alloy make the substance harder
Because different sized atoms of metals distort the layers in the structure making it more difficult for them to slide over each other
What do shape memory allows do after being deformed and name an example
Return to their original shape, Nitinol used in dental braces
What defines the properties of a polymer
What they are made from and the conditions under which they are made
Thermosoftening polymers consist of
Individual tangled polymer chains
Thermosetting polymers consist of
polymer chains with cross-links between them so they do not melt when heated
Nanoscience refers to structures that are
1-100nm in size
Is it thermosetting or softening that can be melted easiliy
thermosoftening