Bonding, Structure And Properties Of Matter Flashcards
Ions
Charged particles
Full outer shells
Metal forming ions
Lose electrons from outer shell to form positive ions
Non metals forming ions
Gain electrons into outer shell to form negative ions
Ionic bonding
Metal and non metal
Metal atom loses electrons and non metal gains these electrons
These oppositely charged ions are strongly attracted to one another by electrostatic forced
Ionic compounds
Have giant ionic lattice structure
Ions form a closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between oppositely charged ions in all directions in the lattice
Ionic compound properties
High melting and boiling points due to many strong bonds between ions
Takes lots of energy to overcome this attraction
When solid ions are held in place so can’t conduct electricity
Dissolve easily in water
Ions separate and are all free to move in the solution so they’ll carry electric current
Covalent bonding
Non metal atoms bond together
Share electrons
The positively charged nucleus of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces, making covalent bonds very strong
Properties of simple molecular substances
Substances containing covalent bonds usually have simple molecular structures
The atoms within the molecules are held together by very strong covalent bonds
The forever of attraction between these molecules are very weak
Low melting and boiling point because all you have to do is break the feeble intermolecular forces
Mostly gases or liquids at room temp
Intermolecular forces get stronger as molecules get bigger
Don’t conduct electricity because they aren’t charged so there’s no free electrons or ions
Polymers
Lots of small units linked together to form a long molecule that had repeating sections
All atoms are joined by strong covalent bonds
Intermolecular forces between polymer molecules are larger than between simple covalent bonds so more energy is needed to break them meaning most are solid at room temp
Intermolecular forces are still weaker than ionic or covalent bonds so have lower boiling points than ionic or giant molecular compounds
Giant covalent structures
All atoms are bonded to each other by strong covalent bonds
High MP and BP as a lot of energy is needed to break covalent bonds between the atoms
Don’t contain charged particles so don’t conduct electricity
Diamond, graphite, silicon dioxide
Diamond
Each carbon atom forms four covalent bonds in a very rigid giant covalent structure
Graphite
Each carbon atom forms three covalent bonds to create layers of hexagons
Each carbon atom also has one delocalised electron
Silicon dioxide
Silica
What sand is made of
Each grain of sand is one giant structure of silicon and oxygen
Allotropes
Different structural forms of the same element in the same physical state
What are allotropes of carbon?
Diamond
Graphite
Graphene
Buck minster fullerene
Diamond properties
has a giant covalent structure, made up of carbon atoms that each form four covalent bonds This makes diamond really hard
Those strong covalent bonds take a lot of energy to break and give diamond a very high melting point
It doesn’t conduct electricity because it has no free electrons or ions.
Graphite properties
in graphite, each carbon atom only forms three covalent bonds creating sheets of carbon atoms arranged in hexagons.
There aren’t any covalent bonds between the layers - they’re only held together weakly, so they’re move over each other. This makes graphite soft and slippery, so it’s ideal as a lubricating material.
Graphite’s got a high melting point-the covalent bonds in the layers need loads of energy to break.
Only three out of each carbon’s four outer electrons are used in bonds, so each carbon atom has one electron that’s delocalised (free) and can move. So graphite conducts electricity and thermal energy.
Graphene properties
Graphene is a sheet of carbon atoms joined together in hexagons.
The sheet is just one atom thick, making it a two-dimensional compound.
The network of covalent bonds makes it very strong.
It’s also incredibly light, so can be added to composite materials to improve their strength without adding much weight.
Like graphite, it contains delocalisesd elecrons so can conduct electaicity through the whole structure. This means it has the potential to be used in electronics.
Fullerenes
Molecules of carbon shaped like closed tubes or hollow balls
Mainly made up of atoms arranged in hexagons but can also contain pentagons or heptagons
They can be used to cage other molecules
This could be used to deliver as drug into the body
Have huge surface areas so could help make great industrial catalysts - individual catalysts could be attached to the fullerenes
Also make great lubricants
Buckminster fullerene
C60
Forms a hollow sphere containing 20 hexagons and 12 pentagons
Nanotubes
1) Fullerenes can form nanotubes -tiny carbon cylinders.
The ratio between the length and
the diameter of nanotubes is very high
Nanotubes can conduct both ectricity and thermal energy (heat)
They also have a high tensile strength (‘they don’t break when they’re stretched)
Technology that uses very small particles such as nanotubes is called nanotechnology.
Nanotubes can be used in electronics or to strengthen materials without adding much weight such in tennis racket frames.
What substances have high melting and boiling points due to strong bonds?
Ionic compounds, metals and giant covalent structures
Why does ions bonding work?
Because they end up with opposite charges so attract
What is a metallic bond?
The attraction between the positive ions and the delocalised electrons
