Topic 1 - Atomic Structure and the Periodic Table Flashcards
How big are atoms
0.1 nanometers (1 x 10^-10)
What is the nucleus
-Middle of the (almost whole mass of atom is concentrated here)
-Contains protons and neutrons
-Radius of 1 x 10^-14m
-Positive charge because of protons
What are electrons
-Around the nucleus in electron shells
-Tiny and negatively charged
-Have virtually no mass
What is the relative mass of each particle
Proton - 1
Neutron - 1
Electron - Very small
What is the charge of each particle
Proton - +1
Neutron - 0
Electron - -1
Why are atoms are neutral
Have the same number of protons and electrons so the charges cancel out
What is an ion
An atom that has lost or gained electrons so has an overall charge
What is the atomic number of an atom
How many protons there are (bottom of nuclear symbol)
What is the mass number of an atom
The total number of protons and neutrons in the atom (top of the nuclear symbol)
What particle decides what element an atom is
The number of protons in the nucleus
What are elements
If a substance only contains atoms with same number of protons
What are isotopes
Different forms of the same element which have the same number of protons but different number of neutrons so they have the same atomic number and different mass number
What is relative atomic mass
An average mass taking into account the different masses and abundances of all the isotopes that make up the element
What is the equation for relative atomic mass
sum of (isotopes abundance x isotope mass number) / sum of abundances of all the isotopes
What are compounds
Substances formed with two or more elements held together by chemical bonds
Why can mixtures be easily seperated
There’s no chemical bonds between the parts of a mixture
Outline how to do paper chromatography
- Draw a line near the bottom of a sheet of filter paper (use pencil)
- Add a spot of ink to the line and place the sheet in a beaker of solvent
- The solvent used depends on what’s being tested. Some dissolve in water but sometimes other solvents, like ethanol are needed
- Make sure ink isn’t touching solvent
- Place a lid on top of the container to stop the solvent evaporating
- Solvent seeps up paper, carrying the ink with it
- Each different dye will move at a different rate so the dyes will separate out
- If any of the dyes is insoluble it will stay on the baseline
- When the solvent has reached nearly the top take the paper out of the beaker and leave it to dry
- The end result is a pattern of spots called a chromatogram
When is filtration used
-If a product is an insoluble solid that needs to be separated from a liquid reaction mixture
-Purification (solid purities in a reaction can be separated)
What are the two methods for separating soluble salt from a solution
Evaporation and crystallisation
Outline evaporation for separating a soluble salt from a solution
-Poir solution into evaporating dish
-Heat slowly and the solvent will evaporate and the solution will get more concentrated. Eventually crystals will start to form.
-Keep heating the dish until all you have left are dry crystals
Outline how to use crystallisation to separate salt from a solution
-Pour solution into evaporating dish and gently heat the solution. Some will evaporate and the solution will get more concentrated
-Once solvent has evaporated or when crystals start to form, remove dish from heat and leave the solution to cool
-The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
-Filter the crystals out Of the solution and leave them in a warm place to dry or a drying oven, or a desiccator
How to separate rock salt
-Grind the mixture to make sure the salt crystals are small
-Put mixture into water and stir. The salt will dissolve, but the sand won’t
-Filter the mixture and the grains of sand won’t fit so they will collect on the paper. The salt passes through the paper we if it’s a part of the solution.
-Evaporate the water from salt so that it forms dry crystals
Outline simple distillation
-The solution is heated. The part of the solution that has the lowest boiling point evaporates first
-The vapour is then cooled, condensed in the condenser and is collected
-The rest of the solution is left behind in the flask
What is the problem with simple distillation
You can only use it to separate things with very different boiling points - if the temperature goes higher than the boiling point of the substance with the higher boiling point, they will mix again
When is fractional distillation used
If you need to separate out a mixture of liquids
Outline fractional distillation
-Put your mixture in a flask and put a fractioning column on top and then heat it
-The different liquids will all have different boiling points so they will evaporate at different temperatures
-The liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column
-Liquids with higher boiling points might also start to evaporate. But the column is cooler towards the top. So they will only get part of the way up before condensing and running back down towards the flask
-When the first liquid has been collected you raise the temperature until the next one reaches the top
What is the plum pudding model
A model that shows atoms to be a ball of positive charge with electrons stuck in it
What did Rutherford expect to happen during the alpha particle scattering experiment
The particles to pass straight through the sheet or be slightly deflected at most. This was because of the positive charge of each atom was thought to be very spread out through the pudding of the atom