Atomic Structure and Periodic Table

• What does an atom contain?

  protons, neutrons, electrons
• Radius of an atom

  0.1 nanometers
• What is the nucleus of a atom

  Middle of an atom that contains protons and neutrons and is positively charged
• radius of the nucleus of an atom

  1x10^-14m
• What are electrons?


  Negatively charged particles, that orbit the nucleus in electron shells and have no mass
• What is the relative mass and charge of a proton?

  Relative mass:1

  Charge:+1
• What is the relative charge and mass of a neutron?

  Relative mass:1

  Charge:0
• What is the relative mass and charge of a electron?

  Relative mass: very small

  Charge:-1
• What is the number of protons equal to?

  number of electrons
• What are elements?


  A substance that only contains atoms with the same number of protons
• What is an isotope?


  Different forms of an element which have the same number of protons but different number of neutrons
• Relative atomic mass formula

  Sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes
• What are compounds?


  Substances formed from two or more elements in which atoms are in fixed proportions and are held together by chemical bonds
• Properties of compounds are...

  different from the properties of the elements that make them up.
• Key compound formulas


  Carbon dioxide- CO2

  Ammonia- NH3

  Water-H2O

  Sodium chloride-NaCl

  Carbon monoxide- CO

  Hydrochloric acid- HCL

  Calcium chloride- CaCl

  Sodium carbonate- Na2CO3

  Sulfuric acid- H2SO4
• How are chemical changes shown?

  chemical equations
• Mixtures


  A combination of two or more substances that are not chemically bonded and they can include elements or compounds
• Paper Chromatography - Method

  1) Draw a pencil line near the bottom of a sheet of filter paper

  2) Add a spot of ink to the line & place the sheet in a beaker of solvent e.g. water - the solvent used depends on what's being tested - some compounds dissolve well in water, but sometimes other solvents e.g. ethanol are needed

  3) Ensure the ink isn't touching the solvent - you don't want it to dissolve

  4) Place a lid on top of the container to stop the solvent evaporating

  5) The solvent seeps up the paper, carrying the ink with it

  6) Each different dye in the ink will move up the paper at a different rate so that the dyes will separate out - each dye will form a spot in a different place, 1 spot per dye in the ink

  7) If any of the dyes in the ink are insoluble in the solvent used, they'll stay on the baseline

  8) When the solvent has nearly reached the top of the paper, take the paper out of the beaker & leave it to dry. The end result is known as a chromatogram.
• What is filtration used for?

  To separate an insoluble solid from a liquid
• Two ways of separating solids from solutions

  Evaporation and crystallisation
• Evaporation method


  1. Pour the solution into an evaporating dish.

  2. Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually, crystals will start to form.

  3. Keep heating the evaporating dish until all you have left is dry crystals.
• Crystallisation method


  1)pour the solution into an evaporating dish and gently heat the solution. Some of the solvent will evaporate and the solution will get more concentrated.

  2)Once some of the solvent has evaporated or when you see crystals start to form(point of crystallisation)remove the dish from the heat and leave the solution to cool

  3)The salt should start to form crystals as it becomes insoluble in the cold highly concentrated solution.

  4)Filter out the crystals from the solution and leave them to dry.
• Filtration and crystallisation of rock salt

  1) grind the mixture to make the salt crystals small to help dissolve easily

  2) put the mixture in water and stir. The salt will dissolve but the sand won't

  3) filter the mixture. Sand collects on the filter paper whilst the salt passes through and is part of the solution

  4) evaporate the water from the salt to from dry crystals
• What is simple distillation used for?


  Separating out a liquid from a solution
• Simple Distillation - Method

  1) The solution is heated. The part of the solution that has the lowest boiling point evaporates first

  2) The vapour is then cooled, condensed & is collected

  3) The rest of the solution is left behind in the flask
• Problems of simple distillation

  Can only separate liquids with very different boiling points
• What is fractional distillation used for?

  To separate a mixture of liquids with similar boiling points
• Fractional distillation method


  1) Put your mixture in a flask & stick a fractionating column on top. Then you heat it

  2) The different liquids will all have different boiling points - they'll evaporate at different temperatures

  3) 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

  4) Liquids with higher boiling points might also start to evaporate, but the column is cooler towards the top, therefore they will only get part of the way up before condensing & running back down towards the flask

  5) When the first liquid has been collected, you raise the temperature until the next one reaches the top
• Who described atoms as solid spheres?

  John Dalton
• plum pudding model of the atom


  atoms are balls of positively charged material with negative electrons scattered through out
• Who made the plum pudding model?

  JJ Thomson, 1897
• What did Rutherford do?

  In 1909 he conducted the alpha particle scatter experiment where they fired positive alpha particles at a thin sheet of gold foil.
• What did they discover from the alpha scattering experiment?

  Came up with the nuclear model where there is a tiny positive charged nucleus at the centre where most of the mass is concentrated. A cloud of negative electrons surrounds this nucleus meaning most of the atom is empty space. This model was founded due to alpha particles being deflected as they came near the concentrated positive nucleus
• Bohr's Nuclear Model


  Where electrons orbit the nucleus in fixed shells and aren't anywhere in between. Each shell is a fixed distance from the nucleus
• Who founded the proton?

  Rutherford
• Who founded the neutron?

  James Chadwick
• How many electrons can the first shell hold?

  2 electrons
• How many electrons are in the outer shell?

  8 electrons
• What were two ways to categorise elements?

  By their physical properties and their atomic weight
• Who created the periodic table ?

  Dmitri Mendeleev in 1869