C1-Atomic Structure and the Periodic Table

• Atoms have a neutral charge
• Protons have a relative charge of +1
• Protons have a relative mass of 1
• Neutrons have relative charge of 0
• Neutrons have a relative mass of 1
• Electrons have a relative charge of -1
• Electrons have a relative mass of 0
• Atomic number is the number of protons in an atom
• Mass number is the number of protons and neutrons in an atom
• John Dalton - atoms were thought to be tiny, indivisible spheres
• JJ Thomson discovered the electron
• JJ Thomson - Plum pudding model where it was suggested that the atom was a ball of positive charge with negative electrons embedded in it
• Alpha scattering experiment wass when scientist fired small, positively charged charged particles at a piece of gold foil only a few atoms thick.From this experiment, they expected the alpha particles to travel straight through the gold foil but some were deflected
• From this experiment  Rutherford concluded that:

  1. The mass of an atom is concentrated in the nucleus
  2. The nucleus is positively charged
• Ernest Rutherford - Nuclear Model where the atom is made up of a positively charged nucleus surrounded by a cloud of negatively charged electrons
• Niels Bohr - proposed that electrons orbit the nucleus in shells/energy levels
• James Chadwick - provided for a neutral particles called a neutrons.Protons and neutrons are in the nucleus, and electrons orbit the nucleus in shells
• Isotopes are atoms of the same element which have the same number of protons but a different of neutrons
• Relative atom mass calculation :

  sum of (isotope abundance x isotope mass number)/ sum of abundance of all the isotopes
• Compounds are substances formed from two or more elements that are chemically combined in fixed proportions
• Mixtures are substances that consist of two or more elements or compounds not chemically combined together
• A solution is a mixture of a liquid and one or more dissolved solids
• A solvent is a liquid that dissolves certain solutes to make a solution
• A solute is a solid that can be dissolved in a liquid to make a solution
• Soluble means it can be dissolved in a given liquid
• Insoluble means it can not be dissolved in a given liquid
• Practical : Chromatography

  1. Draw a pencil line near the bottom of the filter paper as pencil is insoluble
  2. Add a spot of ink to the line
  3. Add the filter paper in the solvent making sure the ink is not in contact with the solvent
  4. As the solvent travels up the paper,it will carry the ink with it and will separate out at different rates
  5. Calculate the Rf value for the spot which is distance travelled by the substance / distance travelled by the solvent
• Practical : Filtration

  1. A filter paper is placed in a funnel above a beaker
  2. The mixture of insoluble solid and liquid is poured into the filter funnel
  3. The filter paper will only allow liquid particles and soluble solids to pass
  4. The liquid that passes through into the beaker is called the filtrate
  5. Insoluble solids do not pass through the filter paper and are left behind as a residue
• Practical : Evaporation

  1. Pour the solution in an evaporating dish
  2. Slowly heat the solution using a bunsen burner
  3. Continue heating the evaporating dish until you are left with dry crystals
• Practical : Crystallisation

  1. Pour the solution in the evaporating dish and gently heat the solution
  2. Once some of the solvent has evaporated or crystal start forming remove the dish and allow it to cool
  3. The salt should form crystals as it becomes insoluble in the cold
  4. Filter the crystals out of the solution and leave them in a warm place to dry
• Simple distillation separates a liquid from a solution
• Fractional distillation separates a mixture of liquids
• Practical : Distillation

  1. Slowly heat the solution and the part of the solution that has the lowest boiling point evaporates
  2. The vapour passes through the condenser and turns back to a liquid form and is collected
  3. The rest of the solution is left behind in the flask
• Electronic Configuration :

  • in the first shell there are only 2 electrons
  • in the second shell there are only 8 electrons
  • in the third shell there are only 8 electrons
• Changes Mendeleev made to the Periodic Table :

  • Mendeleev left gaps in the periodic table for undiscovered elements
  • Mendeleev switched the order of elements based on their chemical properties, not their atomic weight
• Metals are :

  • Strong (hard to break)
  • Malleable (easily bent or shaped )
  • Good conductor of electricity and heat
  • High melting and boiling points
• • Non metals are :
  • Brittle (easy to break)
  • Less dense
  • Poor conductors of heat and electricity
  • Are not always solid at room temperature
• • Transition metals:
  • Dense,strong and shiny
  • Good conductors of heat and electricity
  • More than 1 ion
  • Colourful
• As you go down group 1, the reactivity increases as the outer electron is more easily lost as the attraction between the nucleus and the electrons decrease
• As you go down group 1, the melting and boiling points decrease