SC5-7 Flashcards
What are ions?
An atom or group of atoms with an electrical charge due to the gain or loss of electrons.
Why do atoms lose or gain electrons?
They’re trying to get a full outer shell (stable electronic structure)
What are positive and negative ions called?
+ = cations
- = anions
When do negative ions (anions) form?
When atoms gain electrons - they have more electrons than protons.
When do positive ions (cations) form?
When atoms lose electrons - they have more protons than electrons.
What groups are the most likely to form ions?
1&2 and 6&7
What ions do group 1&2 form?
They lose electrons so form positive ions.
What ions do group 6&7 form?
They gain electrons to form negative ions.
What happens to the electrons if a metal and non-metal react together?
The metal atom loses electrons to form a positive ion (cation) and the non-metal gains the electrons to form a negative ion (anion).
What is ionic bonding?
Transfer of electrons.
What diagram is used to show how ionic compounds are formed?
Dot and cross.
What structure do ionic compounds have?
They ions form a closely packed regular lattice structure.
What are the similar properties between ionic compounds?
- Strong electrostatic forces of attraction between oppositely charged ions.
- They have a high melting and boiling point due to the strong attraction between the ions. It takes a large amount of energy to overcome this attraction.
- Solid ionic compounds don’t conduct electricity because the ions are fixed in place and can’t move, but when the ions are free to move, they will carry an electrical current.
- Many dissolve easily in water. The ions separate and are all free to move in the solution, so they’ll an electrical current.
What is a covalent bond?
Its a strong bond that is formed when a pair of electrons is shared between two non-metal atoms.
What diagram is used to show covalent bonding?
Dot and cross.
What are the properties of covalent bonds?
- Held together by strong covalent bonds, but the forces of attraction between the molecules is weak.
- The melting and boiling points are low because of the weak intermolecular forces.
- They don’t conduct electricity because they don’t contain any free electrons or ions.
- Most are soluble.
- Most molecular substances are gases or liquids at room temp.
What are the properties of giant covalent structures?
- The atoms are bonded together by strong covalent bonds.
- They have a very high melting and boiling point.
- They generally don’t contain charged particles, so they don’t conduct electricity.
- They aren’t soluble in water.
What are some examples of carbon-based giant covalent structures?
Diamond
Graphite
Graphene
Fullerenes
What are the properties of diamond?
- Its made up of a network of carbon atoms that each form four covalent bonds.
- The strong covalent bonds take lots of energy to break, so it has a high melting point.
- The atoms are in a rigid lattice structure, making diamond really hard.
- Doesn’t conduct electricity as there are no free electrons or ions.
What are the uses of diamond?
Strengthen cutting tools.
Jewellery
What are the properties of graphite?
- Each atom only forms 3 covalent bonds, creating sheets of carbon atoms arranged in hexagons.
- The layers are only held together by weak intermolecular forces, so the layers are free to move over each other. This makes it soft and slippery.
- High melting point due to the covalent bonds.
- It conducts electricity because each carbon atom has 1 delocalised electron.
What are the uses of graphite?
Pencils
Batteries
Lubricants
What are the properties of graphene?
Its one layer of graphite - very thin.
Its a sheet of carbon atoms joined together in hexagons.
Its only one atom thick making it 2-dimensional.
What are the uses of graphene?
Technology - phone screens.
What are fullerenes?
What are their properties?
They’re molecules of carbon shaped like closed tubes or hollow balls.
They’re mainly made up of carbon atoms arranged in hexagons, but can also contain pentagons or heptagons.
They have a huge surface area.
What are the uses of fullerenes?
They can be used to ‘cage’ other molecules. The fullerene structure forms around another atoms or molecule, which is then trapped inside.
- This could be used to deliver a drug directly to cells in the body (cancer).
- Huge surface area = great industrial catalysts.
Give an example of a fullerene?
Buckminsterfullerene - hollow sphere.
What happens in metallic bonding?
The electrons in the outer shell of the metal atoms are delocalised. There are strong forces of electrostatic attraction between the positive metal ions and the shared negative electrons.
These forces of attraction hold the atoms together in a regular structure and are known as metallic bonding
What does delocalised mean?
Free to move around.
What are the properties of metals?
Good conductors of heat and electricity. Generally shiny and smooth. Most solid at room temp. They aren’t soluble in water. Very high melting and boiling point. Malleable. Durable, strong and flexible.
How are metals malleable?
The layers of atoms in a pure metal can slide over each other.
This means they can be hammered or rolled into flat sheets.
What are the properties of non-metals?
Have a variety of different structures and a wide range of chemical and physical properties. They tend to be dull looking, More brittle, Have lower boiling points, Generally not solids at room temp, Generally don’t conduct electricity Often have a lower density.
What is an ionic bond?
A strong electrostatic force of attraction between oppositely charged ions.
What is a metallic bond?
Electrostatic attraction between metal ions and the delocalised electrons.
