Chemistry: Topic 1

• Name the three subatomic particles

  protons, neutrons, electrons

  
• What is the radius of the nucleus

  1x10^-14m

  Less than 1/10 000 of the radius of the atom
• State the charge and relative mass of the three subatomic particles

  
• What are isotopes?


  atoms with the same number of protons but different number of neutrons
• How do you calculate relative atomic mass? (Ar)


  (% of Isotope 1 x mass of Isotope 1) + (% of isotope 2 x mass of Isotope 2) / 100
• Copper has two stable isotopes. Cu-63 has an abundance of 69.2% and Cu-65 has an abundance of 30.8%. Calculate the relative atomic mass of copper to 1 decimal place.

  1) (69.2 x 63) + (30,8 x 65) / 69.2 + 30.8

  2) 4359.6 + 2002 / 100

  3) 6361.6 / 100

  4) 63.616

  final answer = 63.6
• How many atoms are in one particle of Na2CO3?

  2 sodium atoms

  1 carbon atom

  3 oxygen atom

  final answer = 6 atoms
• A compound has a formula (Al2(SO4)3)

  Name the elements and state how many atoms of each element are represented in its formula.

  2 aluminium atoms

  3 sulphur atoms

  12 oxygen atoms

  17 in total
• Balance- Fe + Cl2 —> FeCl3

  2Fe + 3Cl2 --> 2FeCl3
• Hydrogen and oxygen molecules are formed in a reaction where water splits apart.

  For this reaction: a) State the word equation b) give a balanced symbol equation.

  a) Hyrogen + Oxygen --> water

  b) 2H2 + O2 = 2H2O
• 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
• What is the mobile phase in chromatography?

  Where the molecules can move. This is always a liquid or a gas
• evaporation practical (soluble salt from a solution)


  1) pour solution into evaporation dish

  2) slowly heat solution. the solvent will evaporate and the solution will get more complicated. Eventually crystals start to form

  3) Keep heating the evaporating dish until all you have left are dry crystals
• Crystallisation practical


  1) pour solution in evaporating dish and gently heat to evaporate some water so solution gets more concentrated

  2) Once some of solvent has evaporated or crystals start to form, remove dish from heat and leave to cool

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

  4) filter the crystals out and leave them in a warm place to dry
• 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
• 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 highest boiling point, they will mix again
• 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
• The history of the atom

  - Neil Bohr


  He proposed that electron orbit the nucleus in fixed shells and aren't anywhere in-between.

  Each shell is a fixed distance from the nucleus.

  
• Give the electronic structure of a) aluminium - 13 b) argon - 18

  a) 2,8,3

  b) 2,8,8
• In the early 1800s elements were arranged by atomic weight.

  What were the obvious ways to categories elements.

  1 - physical and chemical properties

  2- atomic weight
• Describe two changes Mendeleev made to the early periodic table.

  1. He put elements MAINLY in order of atomic weight but did switch that order if the properties meant it should be changed

  2. He left gaps for undiscovered elements.
• Using a periodic table, state how many electrons beryllium has in its outer shell.

  2

  
• Chlorine reacts in a similar way to bromine suggest why?


  They are in the same group of group 7 and they have the same amount of electrons on it outer shell.
• Sodium readily forms 1+ ions. Suggest what ions potassium forms and explain why.

  Potassium forms a 1+ ion as it is in group as sodium so it reacts differently.
• What ions do metals form?

  positive ions
• Physical Properties in metals.


  - have metallic bonding

  - Strong (hard to break), but can bent or hammered

  into different shapes (malleable)

  - great at conducting heat an electricity

  - high boiling and metal points
• Physical properties in non-metals


  - don't have metallic bonding

  - more brittle

  - aren't always solids at room temperature

  - don't generally conduct electricity

  - low density
• Properties of transition metals


  - shiny

  - form more than one ion. e.g copper forms Cu+ and Cu2+

  - transition metal ions are often coloured, so compounds that contain them are colourful. eg Potassium chromate (VI) which is yellow.

  - make good catalysts
• Group 1 - reaction with chlorine


  - react vigorously when heated in chlorine gas to form white metal chloride salts.

  - as reactivity increases the reaction with chlorine gets more vigorous.
• Group 1 - reaction with oxygen


  - they form a metal oxide

  - Lithium forms lithium oxide (Li2O)

  - Sodium form a mixture of Sodium oxide and Sodium peroxide (Na2O2)
• Give the balanced symbol equation for the displacement reaction between bromine and sodium iodide.

  Br2 + 2NaI --> 2NaBr + I2
• Explain the trends in group 0?

  As you do down group 0, the boiling points increase due to an increase in the number of electrons in each atom leading to greater intermolecular forces between them which they need to over come.
• Neon is a gas at 25°C. Predict what state helium is at this temperature.


  Helium has a lower boiling point than neon as it is further up the group.

  So, helium must also be 25'C

  
• Radon and krypton have boiling points of -62°C and -153°C respectively. Predict the boiling point of xenon.


  Xenon comes in between radon and krypton in the group so you can predict that boiling point would be halfway betweem their boiling points

  (-153) + (-62) = -215

  -215/2 = - 107.5 = -108'C
• Argon is very unreactive. Using your knowledge of its electronic structure, explain why.

  Argon has a full outer shell so is electronically stable and does not lose or gain electrons.