Bonding Flashcards
What is iconic bonding?
An ionic bond is formed when electrons are lost and gained by two or more atoms.
When atoms lose electrons they become positive ions
When atoms gain electrons they become negative ions
Ionic bonds are formed between metals and non - metals.
Why do they have high melting points and boiling points?
Strong attraction between the ions and takes a large amount of energy to overcome this attraction
Why do solid iconic compounds don’t conduct electricity?
The ions are fixed in place and can’t move.
However, when it melts, the ions are free to move and will carry an electrical current.
What is a covalent bond?
Forms when two non-metal atoms share a pair of electrons
The electrons involved are in the outer shells of the atoms.
An atom that shares one or more of its electrons will complete its outer shell.
What are the properties of a simple molecular substances?
Low melting and boiling points
- this is because little energy is needed to break the weak intermolecular forces
Do not conduct electricity
- this is because they do not have any free electrons or an overall electric charge.
What are simple molecular substances?
Contain only a few atoms held together by covalent bonds.
An example is carbon dioxide (CO2), the molecules of which contain one atom of carbon bonded with two atoms of oxygen.
What are giant molecular substances?
Contain very many atoms , each joined to adjacent atoms by covalent bonds .
The atoms are usually arranged into giant regular lattices - extremely strong structures because of the many bonds involved.
What are properties of giant molecular substances?
Very high melting points
– this is because a lot of strong covalent bonds must be broken. Graphite, for example, has a melting point of more than 3,600°C.
Variable electrical conductivity
- diamond does not conduct electricity -doesn’t contain charged particles, whereas graphite contains free electrons so it does conduct electricity.
What is diamond and it’s properties?
Hard
- Each carbon atom is joined to four other carbon atoms, forming a giant covalent structure.
- Strong covalent bonds are difficult to break.
High Melting and Boiling Point
- Giant Covalent Structure so there are many strong covalent bonds that needs to be broken down.
- Large amounts of heat energy is needed to overcome forces and break down bonds.
Does not Conduct Electricity
- All four valence (outer-shell) electrons are used in covalent bonds so there are no delocalised electrons that are mobile to conduct electricity
Uses:
- Cutting Tools
- Jewellery
What is graphite and its properties?
Soft and Slippery
- Graphite is made up of two-dimensional layers of carbon atoms
- Forces of attraction between the layers are weak so the layers easily slide over one another and can easily be separated.
High Melting and Boiling Point
- Within each layer, each carbon atom forms strong covalent bonds with three other carbon atoms in a giant covalent structure so there are many strong covalent bonds that needs to be broken down
- Large amounts of heat energy is needed to overcome forces and break down bonds.
Conducts Electricity
- Only three valence electrons are used in forming covalent bonds
- Fourth electron is delocalised between the layers and free to move parallel to the layers to conduct an electric charge.
Uses:
- Lubricant
- Electrodes for Electrolysis
What is fullerenes?
Fullerenes are molecules of carbon atoms shaped like closed tubes or hollow balls
Mainly made up of carbon atoms arranged in hexagons, but also contain pentagons or heptagons
What is metallic bonding?
Forces of attraction that hold atoms together in a regular structure and are very strong
What are inside metals?
Electrons in the outer shell of metal atoms are delocalised and there are strong forces of electrostatic attraction between the positive metal ions and the sharked negative electrons
What are the properties of metals?
Found on the left side of the periodic table
Electrical conductors
- because their delocalised electrons carry electrical
charge through the metal
Good conductors of thermal energy
- because their delocalised electrons transfer energy
High melting points and boiling points,
- because the metallic bonding in the giant structure of a
metal is very strong
- Large amounts of energy are needed to overcome the
metallic bonds in melting and boiling
More Dense
- ions in the metallic structure are packed close together
Malleable
- layers of atoms in a pure metal can slide over each other which they can be hammered or rolled into flat sheets
METAL TEND TO LOSE ELECTRONS to gain full outer shells
