Unit 2 Flashcards
It causes them to fatigue and stop contracting efficiently
The magnesium atom transfers 2 electrons to the oxygen atom. A magnesium ion with a 2+ plus charge forms, and an oxide ion with a 2- charge forms. The Oppositely charged ions are attracted to each other by electrostatic attraction.
Discuss the uses and limitations of dot and cross diagrams
Dot and cross diagrams show charge of the ions, arrangement of electrons, which atoms are electrons in an ion originally come from
However. In they do not show the structure of the compound, or correctly represent the size of the ions
Name the type of structure that ionic compounds have
A giant ionic lattice
Describe the structure of a crystal of sodium chloride
Sodium chloride contains positive sodium ions and negative chloride ions that are arranged in a regular lattice. The oppositely charged ions are held together by electrostatic forces acting in all directions.
Give an advantage and disadvantage of a 3D diagram
The diagram shows the 3D arrangement of the ions
A diagram has incorrect sizes of ions
Potassium bromide is an ionic compound. Suggest why potassium bromide have a low electrical conductivity as a solid
The ions are in fixed positions in the lattice and so are not able to move and carry a charge through the solid
Potassium bromide is an ionic compound. Suggest why potassium bromide has a good electrical conductivity in a solution.
The ions dissolve and can move around freely to carry charge from place to place
What is a disadvantage of dot and cross diagrams
Doesn’t show how atoms are arranged in space
Does not show molecular sizes
Advantages and disadvantages of displayed formula die
Shows how all the atoms are connected in a simple way, doesn’t show the 3D structure of the molecule
Advantages and disadvantages of dot and cross diagrams
Shows where the electrons originally came from but doesn’t show the 3D structure of a molecule
Advantages of 3D model diagrams
Shows how all the atoms are arranged in space, but it becomes complicated for large molecules
At room temperature, iodine is a solid. Explain with reference to the forces between molecules, why this is unusual for a simple molecular substance.
Simple molecular substances have weak forces between molecules so not much energy is needed to overcome them
Why can’t iodine conduct electricity
the electrons aren’t free to move and won’t carry a charge
Suggest why the boiling point of methane is lower than that of butane(5)
When methane boils, forces between the molecules that overcome and it turns from a liquid into a gas. Methane is a smaller molecules and butane so the forces between the molecules are weaker and less energy is needed to overcome them
Picture of molecule of propane. Is this molecule likely to be solid, liquid or gas
Solid because this molecule is very large so the inter molecular forces are strong and need energy to be broken
Explain how atoms in metallic bonding are held together
Strong electrostatic attraction between the delocalised electrons on the positive metal ions
Explain how the structure in metals means they are able to be bent and shaped
Metallic structures have layers of ions which can slide over each other
Explain why it’s usually easier to change the shape of a pure metal than an alloy
Atoms of different elements have different sizes. Adding atoms of a different size to a pure metal distorts the layers making it harder for them to slide over one another
Describe how the particles in a substance are represented in particle theory
As solid spheres
What two physical processes can particle theory be used to explain
Melting, boiling, freezing, condensing
Explain two ways in which particle theory doesn’t actually represent the particles in a substance
Particles aren’t really spheres
Particles are mostly empty space
It does not show the forces between molecules
What is the surface area to volume ratio
Surface area / volume
How many nano metres is a nano particle
100
What counts is a fine particle
1000 nanometres
State two possible advantages of using nano particles in sun cream
Better skin coverage
Better absorbing UV rays
State two possible disadvantages of using nano particles in sun cream
When they are washed away they can damage the environment
There might be unknown risks which could cause health threats
