Atomic Structure + Periodic Table Flashcards
Relative atomic mass formula
Ram = sum of ( isotope abundance X isotope mass number ) ÷ sum of abundance of all the isotopes
Method of Chromatography
- Draw a line in pencil near the bottom of the filter paper.
- Add a spot of ink at the line.
- Place in a solvent, usually water but sometimes ethanol is used for insoluble substances.
- Make sure the ink doesn’t touch the solvent.
- Solvent moves up the paper, carrying the ink with it.
- Depending on how soluble the different inks are they will move up the paper at a different pace.
- Once the solvent reaches near the top take the paper out and leave it to dry.
The Process of Evaporation
- Pour liquid into evaporating dish
- Slowly heat the solution over a Bunsen burner or in a heat bath.
- Keep heating untill only crystals are left.
This is a quick method and can only be used if a salt doesn’t decompose when heated.
The process of crystallisation
- Pour solution into evaporating dish
- Gently heat the solution up to the point of crystallisation, then remove it from the heat and leave it to cool.
- The salt will start to form crystals as it is insoluble in the cold, highly concentrated solution.
- Filter the crystals out of the solution and dry.
This method is used when salts decompose in high temperatures
Simple Distillation - Practical
- The solution is heated, the part of the solution with the lowest boiling point evaporates first.
- The vapour is then cooled in the condenser and is collected.
- The rest of the solution is left in the flask.
What is Distillation used for ?
Separating a liquid from a solution.
What is a problem with simple Distillation ?
It can only be used to separate things with very different boiling points.
Method of Fractional Distillation.
- Put the mixture in a flask and attach a fractionating column at the top.
- The liquid with the lowest boiling point evaporates first, once the temperature on the thermometer reaches the boiling point of the liquid it will reach the top.
- The vapour will then be condensed in the condenser and collected.
- Liquids with higher boiling points may also start to evaporate however the fractionating column is cooler towards the top so they will condense before they reach the top.
- Once the first liquid has been collected raise the temperature to the boiling point of the next lowest until it reaches the top and repeat until all of the liquids have been separated.
What was the first model of the atom and who created it ?
Atoms were solid spheres, John Dalton
Who created the plum pudding model ?
J J Thomson
What came after the plum pudding model ?
The nuclear model
What experiment lead to the nuclear model and who ?
The alpha scattering experiment lead by Ernest Rutherford+ his student Ernest Marsden.
What did the alpha scattering experiment discover ?
- There is a tiny positively charged nucleus at the centre of the atom.
- Where most of the mass is concentrated.
- There is a cloud of negative electrons surrounding it.
What did Niel B___suggest ?
Bohr
Suggested that all the electrons orbited the nucleus in shells at fixed distances.
What was the problem with Rutherford’s model ?
The cloud around the nucleus would be attracted to the nucleus, causing the atom to collapse.
