Topic 2 Bonding, Structure And Properties Of Mass Flashcards
What is a gas like?
4 points
- Particles are free to move
- State symbol= g
- Can be easily compressed
- expand to fill the shape of the container
What is a liquid like?
3 points
- Particles can flow over each other but are still attracted to each other.
- Changes shape in different containers.
- State symbol= l
What is a solid like?
3 points
- Particles are fixed in place
- Fixed shape and volume
- State symbol= s
What are the limitations of the particle model?
- Not all particles are the same size
- Not all particles are round
- Particles are not solid
What are ions?
Charge particles
When are ions formed?
When atoms lose or gain electrons to form ions to try and get a full outer shell of electrons to become stable.
What do metals do with electrons?
Lose them to become positive ions.
What do non-metals do with electrons?
Gain them and become negative ions
How are the number of electrons lost/gained and the charge relative?
The number of electrons lost or gained is the same as the charge.
E.g.
2 lost electrons= 2+
3 gained electrons= 3-
Which groups of elements are most readily to form ions?
1, 2, 6, 7
How is an ionic bond made?
By the transfer of electrons between a metal and a non-metal.
What happens when a metal and a non-metal react together?
The mental loses electrons to become positively charged and the non-metal gains electrons to become negatively charged.
How are the oppositely charged ions in an ionic bond held together?
Strongly but electrostatic forces.
What sort of diagrams should you use to represent ionic bonds?
Dot and cross diagrams
How do you work out the empirical formula of a dot and cross diagram?
Count up how many atoms there are of each element and balance them out.
How do you work out the empirical formula using a 3D diagram of an ionic lattice?
Use it to work out what ions are in the ionic compound.
What sort of structure do ionic compounds have?
A structure called a giant lattice.
What is a giant lattice?
A 3D structure made by oppositely charged ions held together by electrostatic forces in all directions.
Why are giant lattices in a 3D shape?
Because there is an attraction between every opposite ion.
What are the properties of ionic compounds?
High melting point- to break strong electrostatic forces.
Soluble
Conduct electricity when dissolved in a solution or molten as ions are free to move and carry electric current.
Why are dot and cross diagrams useful for showing ionic compounds?
They show how they are formed.
Why are dot and cross diagrams not useful for showing ionic compounds?
They don’t show the structure of the compound, the size of the ions or how they are arranged.
When is a covalent bond formed?
When non-metal atoms bond together, they share pairs of electrons to make covalent bonds.
What is a covalent bond like?
The positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by strong electrostatic forces, making the covalent bond very strong.
What is a positive of writing the empirical formula for a covalent bond?
It can be written easily and is easy to understand.
Why are dit and cross diagrams useful for showing covalent bonds?
They are useful for showing which atoms the electrons in covalent bond comes from.
Why are diagrams such as:
O-H-O
Good for showing covalent bonds?
They show how atoms are connected in large molecules.
Why are diagrams such as:
O-H-O
Bad for showing covalent bonds?
They don’t show the 3D structure of the molecule or which atoms the electrons in the covalent bonds have come from.
What does the 3D model show of covalent bonds?
The atoms, the covalent bonds and their arrangement.
Why can 3D models showing covalent bonds get confusing?
When there are lots of atoms to include.
They also don’t show where the electrons in the bonds have come from.
What are simple molecular substances?
Substances made up of molecules containing a few atoms joined together by covalent bonds.
What are the properties of simple molecular substances (simple covalent molecules)?
(7)
- Have simple molecular structures
- Held together by very strong covalent bonds but the forces between the molecules are very weak.
- The melting and boiling points of simple molecular substance are very low because you need to break the (weak) intermolecular forces, not the (strong) covalent bonds.
- Most are liquids or gases at room temperature
- As molecules get bigger the strength of the intermolecular forces increase, so more energy is needed to break them.
- Don’t conduct electricity because there is no charge and all electrons are used in bonding so there are no free electrons
- usually soft and brittle
What are polymers?
Long chains of repeating units. In a polymer lots of small units are linked together to form a long polymer that has repeating units.
How are all the atoms in a polymer joined?
Be strong covalent bonds.
How can you draw a polymer easily?
You can draw out the shortest repeating section, called the repeating unit.
How do you find the molecular formula of a polymer?
Write down the molecular format of the repeating units in brackets and put an ‘n’ outside.
What are the intermolecular forces between polymer molecules like?
They are larger than the intermolecular forces between covalent molecules. This means most polymers are solid at room temperature. The intermolecular forces are still weaker than ionic or covalent bonds so they generally have lower boiling points than ionic or giant molecular compounds.
What are polymers, simple molecular substances and giant covalent structures held together by?
Covalent bonds
What sort of molecules are giant covalent structures held together by?
Macromolecules
What are the properties of giant covalent structures?
- All atoms bonded by strong covalent bonds.
- Very high melting and boiling points as lots of energy is needed to break covalent bonds.
- Usually do not conduct electricity (no charged particles and no free electrons)
What are the main examples of giant covalent structures?
Diamond, Graphite, Silicon dioxide
What is the structure of diamond like?
Each carbon atom forms four covalent bonds in a very ridged covalent structure.
What is the structure of graphite like?
Each carbon atom forms three covalent bonds to create layers of hexagons. Each carbon also has one delocalised electron.
What is the structure of silicon dioxide like?
Sometimes called silica, this is what sand is made of. Each grain of sand is one giant structure of silicon and oxygen.
What are allotropes?
Different structural forms of the same element in the same physical state.
What is diamond made up of?
Carbon atoms that form four covalent bonds as there are four electrons in its outer shell) this makes diamond very hard.
Why does diamond have a very high boiling point?
The covalent bonds are very strong.
Why does diamond not conduct electricity?
No free electrons
What is graphene?
A sheet of carbon atoms joined in hexagons (one layer of graphite).