C.3 Flashcards
Why is the particle model limited?
It assumes all particles are solid spheres which is not the case
It assumes there are no forces of attraction between the particles
What happens in ionic bonding?
Ionic bonding is between non metals and metals, as both become ionised. The metal loses electrons to become positively charged and the non metal gains electrons to become negatively charged.
What happens to non metals in ionic bonding?
They become IDE ions (chloride, fluoride, oxide etc)
What does ionic bonding form?
Ionic compounds which form giant strucutres known as giant ionic lattices. Every positive metal ion is fully surrounded by negative non-metal ions.
Why do ionic compounds have a high melting & boiling point?
The electrostatic forces of attraction (ionic bonds) are very strong and require a large amount of energy to break down.
Why can ionic compounds not conduct electricity?
Because the ions are held in fixed positions. They can conduct electricity when melted or dissolved in water - remember the ions are moving and not the electrons.
Why are some elements diatomic?
Elements such as hydrogen are diatomic as they consist of 2 hydrogen atoms covalently bonded together to achieve stability.
What are 4 covalent bonds you need to be able to recognise?
Water (H2O), Ammonia (NH3), Metahne (CH4), Carbon Dioxide (CO2)
What does a double and triple bond mean?
A double covalent bond means there are two pairs of electrons being shared, and a triple bond is where three pairs are shared.
What are Water, Methane and Ammonia known as and what does this mean?
Small covalent molecules - meaning they have a low melting & boiling point and are usually a gas or liquid at room temperature. This is becuase the intermolecular forces between two covalently bonded molecules are very weak.
Why can small covelant molecules not conduct electricity? ⚡️⚡️🤓
As they do not have an overall electric charge
What type of strucrured are diamond and silicon dioxide?
They are giant covalent structures as they contain millions of covalent bonds and are always solid at room temperature as they have high melting and boiling points.
What is diamond?
Millions of carbon atoms covalently bonded which makes it very hard. This is because each carbon atom is bonded to 4 other carbon atoms.
Why do diamonds not conduct electricity?
Because all of it’s outer electrons are in covalent bonds, meaning there are no free electrons to carry charge.
What is graphite?
A allotrope of carbon arranged in layers of hexagonal carbon rings. The rings are not covalently bonded together meaning it is soft and slippery. It is often used as a lubricant in machines.
What are the properties of graphite?
- Soft and slippery
- High melting & boiling point
- Good conductor of heat & electricity
Why does graphite conduct heat and electricity?
Because each atom is only bonded to 3 other carbon atoms, not 4. This means one electron (delocalised electron) is left free to move between the layers and carry a charge.
What is graphene?
A single layer of graphite which is only one atom thick. It is very strong and has the same properties as graphite for the same reasons.
What is a fullerene?
A molecule made up of carbon atoms with hollow shapes. They are arranged in hexagonal rings which may have 5 or 7 carbon atoms.
What was the first fullerene discovered and what are it’s uses?
Buckminsterfullerene (C60) - made of hexagonal or pentagonal rings of carbon atoms
- used as lubricants, catalysts and for pharmaceutical deliveries into the body
What are carbon nanotubes?
Long, cylindrical fullerenes made up of hexagonal rings. ¡Very useful!
They are useful due to their high tensile strength (easily stretched) and their good heat and electricity conduction.
What is a polymer?
A very large molecule formed by conjoining thousands of small identical molecules known as monomers which are usually alkenes.
How are polymers bonded?
Polymers have single covalent bonds, but monomers have double covalent bonds (as they’re alkenes).
How are polymers represented?
Using a repeating unit where the polymer is enclosed in brackets which have like a dash in them to show the polymer repeats beyond the brackets. There is a small n at the bottom right of the closing bracket which represents a large number.
Why are polymers solid at room temp?
Because the intermolecular forces of attraction are relatively strong.
What are the main properties of metals?
They are giant structures arranged in regular layer. The electrons in the outer energy level are delocalised meaning metals are good conductors of electricity and heat.
Why are metallic bonds strong?
Because there is a strong electrostatic attraction between the sea of delocalised electrons and the positive metal ions (as they lost an electron). This means metals have a high boiling & melting point and are great conductors of electricity & heat.
*electrostatic attraction is attraction between something negative and something positive
Why is the structure of metals important?
Their arrangement in regular layers is important as it means they are malleable as the atoms can slide over each other.
Why are alloys useful?
They are harder than pure metals as the different sizes of the atoms distort the layers meaning they cannot slide easily.
Evaluate the dot and cross diagram.
- Very obvious where the electrons are coming from
- Doesn’t show the shape of the molecule
Evaluate the stick diagram.
- It does not show which electron in the bond came from which atom
- It doesn’t show outer electrons which are not in the bond
BUT the 3D stick diagram shows the shape of the molecule
Evaluate the ball and stick diagram.
- Shows giant ionic lattices as it shows the ions in 3 dimensions
- Shows the ions as speead out as opposed to close together
Evaluate space filling diagrams.
- They solve the problem of ions being shown as widely spaced apart
- It can be difficult to see the ions
- Neither this nor the ball and stick diagram show size, giving us a mistaken impression of the sizes of giant ionic structures.
