Topic 1-Atomic Structure and the Periodic Table

Filtration Crystallisation Simple distillation Fractional distillation Chromatography

The concept that an atom was a ball of positive charge with negative electrons embedded in it

A beam of alpha particles was aimed at very thin gold foil and their passage through was detected Some of the alpha particles emerged from the foil at different angles and some even came straight back The positively charged alpha particles were being repelled and deflected by a small concentration of positive charge in the atom (nucleus)

It was concluded that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged

Niels Bohr

He provided the evidence to show the existence of neutrons within the nucleus

0.1nm 1x10^-8cm

1x10^-14 Less that 1/10,000 of that of the atom

They are atoms of the same element with different numbers of neutrons

((isotope 1 mass x abundance) + (isotope 2 mass x abundance)) ÷ 100

Draw line with pencil on filter paper Add spot of ink then place paper in solvent (not touching to avoid dissolution) The solvent will slowly rise, separating the spot into few spots.

Pen ink is soluble and will dissolve in the solvent

It is called a chromatogram

This is to stop the solvent from evaporating

The solution is heated and the part of the solution that has the lowest boiling point evaporates first The vapour is cooled, condenses and is collected The rest of the solution is left behind in the flask

You can only use it to separate things with very different boiling points

Put your mixture in a flask and put a fractionating column on top. Then heat it Liquid boiling points evaporate firsts and once the temperature reached the boiling point of this liquid, it will reach the top of the column where it will condense down. Once the first liquid has evaporated you can raise the temperature until the next one reached the top

The column in cooler at the top and so it will only reach part of the way before condensing back down

Filter paper is folded into a cone and placed at the top of a beaker Then, pour your mixture into the cone. The filter paper will catch the insoluble solid (residue) while the filtrate comes through the paper

Pour solution into evaporating dish and heat solution. Some solvent will evaporate and the solution will become more concentrated Once some solvent has evaporated, remove dish from the heat and leave the solution to cool Salt should start forming crystals as it becomes insoluble in the cold, highly concentrated solution Filter solution to get crystals out and leave them in a warm place to dry or use a drying oven

An apparatus for separating immiscible liquids. Two immiscible liquids of different densities will form two distinct layers in the separating funnel We can run off the bottom layer (greater density) to a separate vessel

Dmitri Mendeleev in 1869

He ordered elements in order of increasing atomic mass

He had left gaps for undiscovered elements He showed elements with similar chemical properties lined up in groups