topic 1 Flashcards
What is a covalent bond?
A shared pair of electrons
Why do elements react?
to form a full outer shell
What is ionic bonding?
the transfer of electrons, from a metal to a non metal
What must you do to demonstrate a charged particle in a dot and cross diagram?
use square brackets and put the charge next to it
What are the key features of a giant ionic lattice?
- Each negative ion is surrounded by a positive and vice versa
- they have very strong electrostatic forces of attraction between molecules
What key features do ionic compounds have?
- High melting and boiling points due to the strong electrostatic forces
- Cannot conduct electricity when solid because the ions are not free to move
- Can conduct when melted or dissolved as the ions are free to move
What is covalent bonding?
when non-metal atoms share one or more pairs of electrons
In which type of diagram do the atoms overlap?
Covalent bonding diagram
What is a stick diagram?
A diagram to represent a covalent compound. One line is one covalent bond.
What are the key properties of small covalent molecules?
- Low melting and boiling points due to the weak intermolecular forces
- Do not conduct electricity as they are not charged
What is the rule for melting and boiling points in terms of covalent compounds?
the more atoms in the compound, the higher the boiling point
What are the key properties of giant covalent molecules?
- Always solid at room temperature due to all the covalent bonds
- High melting and boiling points due to all the covalent bonds
Give 3 examples of giant covalent molecules.
Diamond
Silicon dioxide
Graphite
What are the properties of diamond?
- Formed from carbon and each carbon atom has 4 bonds
- VERY HIGH melting and boiling point
- VERY STRONG
- Cannot conduct electricity as there are not free electron
What are the properties of Silicon dioxide?
- VERY HIGH melting and boiling point
What are the properties of graphite?
- Formed of carbon atoms in hexagonal rings (3 bonds each)
- High melting and boiling point due to many covalent bonds
- Soft and slippery due to lack of covalent bonds between layers
- Conducts electricity and heat as there are delocalised electrons (carbon only makes 3 bonds in graphite, leaving one spare)
Is graphite a metal?
NO
What is graphene?
A single layer of graphite (only an atom thick)
What are the properties of graphene?
- Good conductor due to delocalised electrons
- Extremely strong
What are fullerenes?
Molecules of carbon atoms with hollow shapes
What are carbon nanotubes?
Fullerenes in the shape of a cylinder. They conduct electricity and have high tensile strengt
What happens when metals react?
they lose electrons to achieve a full outer shell, becoming a positive ion.
Where are metals located on the periodic table?
Left and middle
What are the properties of all metals?
- giant structure in layers
- conduct electricity due to delocalised electrons
What is metallic bonding?
Bonding between 2 metals
What does metallic bonding create?
Giant lattice of metal ions in a sea of delocalised electrons
What is a metallic bond?
The electrostatic attraction between metal ions
What are the properties of metals?
- High melting and boiling points
- Good conductors
- Malleable as layers can slide over each other
What is an alloy?
A mixture of two or more metals
What are the differences between pure metals and alloys?
- Alloys are less malleable as there are no clear layers (distorted)
- Alloys are stronger than pure metals
Evaluate a dot and cross diagram
- Can easily tell which electrons are from which atom
- Does not demonstrate the shape of the molecule
Evaluate a stick diagram
- Cannot tell which electron came from which atom
- Does not show other electrons
Evaluate a ball and stick diagram
- Shows shape effectively in 3d
- Is not accurate as ions are actually packed incredibly close together
- Only shows small amount of real structure
Evaluate a space filling diagram
- Demonstrates how close together the ions are
- Can be difficult to understand
- Only shows small amount of real structure
