Atomic structure and the Period Table

• Elements compounds and mixtures 


  •in an element all atoms are the same

  •compounds contain 2 or more elements chemically combined

  •compounds have different properties as there elements

  •mixtures contain compounds or elements that aren’t chemically combined

  •to separate a mixture you can use filtration distillation cystilisation or chromotography

  •a molecule has any compound chemically combined
• Interpreting a Chemical Formula 


  •formulas show how many atoms are in a compound

  •if there’s a bracket in the formula you multiply whatever is inside the bracket
• Filtration and Crystallisation 


  •these are physical separation techniques not chemical

  • can only be used to mixtures

  •filtration is used to separate an insoluble solid from a liquid

  •pour ur mixture into the filter funnel and the filter paper

  •only the liquid will then pass through the filter paper into the conical flask

  •cystilisation is used to seperate a soluble solid from a liquid

  •leave the mixture of the liquid and the soluble solid for a few days by then the liquid would’ve dissolved

  •to speed up crystilisation you can gently heat the solution to evaporate the liquid
• Simple Distillation 


  •evaporate the liquid by heating this turns liquid into vapour

  • then condense the vapour back into liquid form by cooling

  METHOD

  •place liquid and soluble solid into a continuous glass tube

  •a condenser is connected to the tube wich has cold water running through it

  •this keeps the tube cold

  •heat the solution and the liquid starts to evaporate

  •however once it reaches the condenser the coldness causes the vapour to condense turning it back into a liquid

  • leaving us with separated solid and liquid
• Fractional Distillation


  Separates a mixture of liquids that have different boiling points
• Fractional Distillation METHOD

  1. Glass tube connected to fractionating column with glass beads

  2. Gently heat the mixture, both liquids will start to evaporate

  3. When vapours reach the column they start to condense and drip into the flask, then evaporate again

  4. This increases the amount of lower boiling point chemical

  5. Once the thermometer starts to go down, only the lower boiling point chemicals reach the end, then the temp will rise again to the other chemicals' boiling point letting it pass through into another fresh beaker
• Fractional Distillation


  • Separates a mixture of liquids
  • Liquids need to have different boiling points
• Paper Chromotography


  •seperates substances in a mixture

  based on solubility

  METHOD

  •place 2 dots of different pen colours on chromatography paper

  •place the bottom of the paper in a solvent

  •the solvent makes it way up the paper and dissolves the the colours

  •the colours and the solvent will now make there way up the paper

  •if there’s only one spot of certain colour it means it’s a pure colour

  •if a colour now has more then one spot it means it was a mixture of two colours
• Scientists found atoms contain negative particles (electrons)


  1897
• Alpha scattering experiment


  • Used to see if plum pudding model was accurate
• Alpha scattering experiment method


  1. Took a piece of gold foil

  2. Fired tiny particles (alpha particles) at the foil

  3. Alpha particles have positive charge
• Findings from alpha scattering experiment


  • Atoms are mainly empty space
  • Plum pudding model was wrong
  • Centre of atom (nucleus) has positive charge
  • Centre of atom (nucleus) has a lot of mass
• Nuclear model


  New model that replaced the plum pudding model
• Atomic Number and Mass Number 


  •electron equal to proton

  •smaller number (bottom number ) =atomic number tells us protons and electrons

  •larger number is mass number = tells us how many protons and neutrons there are

  •isotopes=atoms of the same element with different number of neutrons

  •ions=atoms with no overall charge because they have lost or gained electrons
• Relative Atomic Mass


  •relative atomic mass(ram) =weighted average between isotopes

  EQUATION

  ram=(mass number of isotope1 x percent abundance of isotope1) +(mass number of isotope2 x percent abundance of isotope 2) divided by 100
• Electron Energy Levels


  first shell=2

  second shell =8

  third shell = 8

  •the number of electrons in the last shell shows us what group it is in periodic table

  •elements with full outer shell in group 0 there called noble gases
• Group 0

  •noble gases are unreactive

  •full outer shell=unreactive

  •relative atomic mass increases= boiling point increases
• Metals 


  •group 1 and 2 are highly reactive metals

  •centre is transition metals

  •when metals react they lose electrons to get a full outer shell

  •metals always form positive ions
• Reactions of Group 1 Metals part 1

  group 1 =alkali metals

  •they all have one electron in its outer shell

  •group 1 metals are soft

  •react rapidly with oxygen

  •as we move down the group 1 the quicker they react
• Group 7 Halogens

  •group 7= non metals

  •if 2 group 7 elements react with eachother they collide and share a pair of electrons this is called a covalent bond

  •as we go down the group the boiling point increases

  •as we go down the group the molecular mass increases
• Group 7 Halogens 


  •form covalent compounds when they react with non metals

  •forms ionic compounds when reacted with metals

  •they form a negative one charge