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Chem GCSE > C.3 > Flashcards

C.3 Flashcards

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1
Q

Why is the particle model limited?

A

It assumes all particles are solid spheres which is not the case
It assumes there are no forces of attraction between the particles

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2
Q

What happens in ionic bonding?

A

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.

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3
Q

What happens to non metals in ionic bonding?

A

They become IDE ions (chloride, fluoride, oxide etc)

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4
Q

What does ionic bonding form?

A

Ionic compounds which form giant strucutres known as giant ionic lattices. Every positive metal ion is fully surrounded by negative non-metal ions.

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5
Q

Why do ionic compounds have a high melting & boiling point?

A

The electrostatic forces of attraction (ionic bonds) are very strong and require a large amount of energy to break down.

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6
Q

Why can ionic compounds not conduct electricity?

A

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.

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7
Q

Why are some elements diatomic?

A

Elements such as hydrogen are diatomic as they consist of 2 hydrogen atoms covalently bonded together to achieve stability.

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8
Q

What are 4 covalent bonds you need to be able to recognise?

A

Water (H2O), Ammonia (NH3), Metahne (CH4), Carbon Dioxide (CO2)

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9
Q

What does a double and triple bond mean?

A

A double covalent bond means there are two pairs of electrons being shared, and a triple bond is where three pairs are shared.

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10
Q

What are Water, Methane and Ammonia known as and what does this mean?

A

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.

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11
Q

Why can small covelant molecules not conduct electricity? ⚡️⚡️🤓

A

As they do not have an overall electric charge

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12
Q

What type of strucrured are diamond and silicon dioxide?

A

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.

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13
Q

What is diamond?

A

Millions of carbon atoms covalently bonded which makes it very hard. This is because each carbon atom is bonded to 4 other carbon atoms.

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14
Q

Why do diamonds not conduct electricity?

A

Because all of it’s outer electrons are in covalent bonds, meaning there are no free electrons to carry charge.

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15
Q

What is graphite?

A

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.

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16
Q

What are the properties of graphite?

A
  • Soft and slippery
  • High melting & boiling point
  • Good conductor of heat & electricity
17
Q

Why does graphite conduct heat and electricity?

A

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.

18
Q

What is graphene?

A

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.

19
Q

What is a fullerene?

A

A molecule made up of carbon atoms with hollow shapes. They are arranged in hexagonal rings which may have 5 or 7 carbon atoms.

20
Q

What was the first fullerene discovered and what are it’s uses?

A

Buckminsterfullerene (C60) - made of hexagonal or pentagonal rings of carbon atoms

  • used as lubricants, catalysts and for pharmaceutical deliveries into the body
21
Q

What are carbon nanotubes?

A

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.

22
Q

What is a polymer?

A

A very large molecule formed by conjoining thousands of small identical molecules known as monomers which are usually alkenes.

23
Q

How are polymers bonded?

A

Polymers have single covalent bonds, but monomers have double covalent bonds (as they’re alkenes).

24
Q

How are polymers represented?

A

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.

25
Q

Why are polymers solid at room temp?

A

Because the intermolecular forces of attraction are relatively strong.

26
Q

What are the main properties of metals?

A

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.

27
Q

Why are metallic bonds strong?

A

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

28
Q

Why is the structure of metals important?

A

Their arrangement in regular layers is important as it means they are malleable as the atoms can slide over each other.

29
Q

Why are alloys useful?

A

They are harder than pure metals as the different sizes of the atoms distort the layers meaning they cannot slide easily.

30
Q

Evaluate the dot and cross diagram.

A
  • Very obvious where the electrons are coming from
  • Doesn’t show the shape of the molecule
31
Q

Evaluate the stick diagram.

A
  • 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

32
Q

Evaluate the ball and stick diagram.

A
  • Shows giant ionic lattices as it shows the ions in 3 dimensions
  • Shows the ions as speead out as opposed to close together
33
Q

Evaluate space filling diagrams.

A
  • 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.

Chem GCSE (9 decks)

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