Structure & Bonding Flashcards
what does bonding mean/describe
how the electrons are distributed to make chemical bonds
what do noble gases do/have
- a full outer shell
- do not need to bond
- exist as single atoms and all exist as gases at room temperature
what is a covalent bond
the attraction between the positive nuclei and a shared pair of electrons
bonding between individual molecules
is not covalent and is weak
why do simple covalent molecules have low melting and boiling points
- attraction between molecules and are very weak
* easy to separate the molecules
carbon exists in two forms / allotropes
diamond and graphite
structure and bonding of diamond
covalent bond, giant molecular lattice structure
bond of carbon as diamond
each carbon atom is covalently bonded to 4 other carbon atoms in a tetrahedral arrangement
uses of diamond
- drill bits to cut through rocks
* jewellery
why are large amounts of energy required to break diamond
- covalent bonds extend through the crystal in a lattice
- each diamond is a single giant molecule
- large numbers of strong covalent bonds
graphite bonding and structure
covalent bond, layer lattice structure
how are the carbon atoms bonded in graphite
carbon atoms bonded covalently to 3 other carbons within layers to form a hexagon of atoms.
why is graphite soft and slippery
only weak intermolecular forces holding layers together so the layers of atoms can easily slide over eachother
what can graphite conduct
electricity
uses of graphite
lubricant, pencils, used as electrodes
what is metallic bonding
attraction between a lattice of positive ions and a sea of delocalised electrons
why are metals strong and have high melting points and boiling points
strong electrostatic attraction between positive ions and negative electrons means that a lot of energy is required to separate the particles from the lattice
why are metals malleable
less energy is required to slide one layer of positive metal ions over another layer
why are metals good conductors of electricity
if a potential difference is applied across a piece of metal, the electrons will move, carrying an electrical current
what is an alloy
mixture of metals
why are alloys stronger and harder than normal metal
always contain atoms of different sizes, which distorts regular arrangements of atoms. makes it more difficult to slide over eachother, so alloys are harder
what is ionic bonding
where ions are held together by strong electrostatic attractions between oppositely charged ions
why are there high b/m points in ionic bonds
strong electrostatic attractions
conductivity in ionic bonds
- can only conduct when melted or dissolved when ions can move
- when solid they cannot move so cannot conduct
why is carbon dioxide a gas at room temperature but silicon dioxide is a solid
- co2 has weak intermolecular forces between molecules
* sio2 is a giant molecular structure that only has strong covalent bonds that have to be broken
why is diamond hard but granite soft
- diamond is a giant molecular lattice. has strong covalent bonds which are hard to break
- graphite is a layer latice. layers of atoms can slide over eachother
what does structure mean/describe
it describes how the atoms, ions or molecules are arranged in a solid
