Atomic structure + Periodic table

• Daltons model of the atom

  Solid sphere that cannot be divided into smaller parts

  Did not include protons, neutrons, or electrons
• Plum pudding model

  Cloud of positive charge with negative electrons embedded in it

  Protons and neutrons has not yet been discovered
• In what order were the sub-atomic particles discovered?

  Electrons -> Protons -> Neutrons
• Alpha scattering experiment

  1. Scientists fired alpha particles at a gold sheet only a few atoms thick
  2. Expected it to just go through, but instead found that some went through, but some were scattered
  3. Concluded that the positive charge and mass of an atom must be held in the centre (the nucleus)
• Nuclear model

  Electrons orbit the nucleus, but not at set distances

  Mass of an atom was concentrated in the charged nucleus
• Bohr model

  Calculated the electrons must orbit at set distances

  Orbits called shells or energy levels
• Order of different models of atoms

  Daltons model

  Plum pudding model

  Nuclear model

  Bohr model
• Relative mass

  Protons: 1

  Neutrons: 1

  Electrons: So small they are considered as 0
• Size of atom + nucleus

  Atom: 1x10^-10

  Nucleus: 1x10^-14
• Drawing atoms

  2 electrons in 1st shell

  8 electrons in 2nd and 3rd shell
• Element: Substances made of one type of atom
• Compound: Different types of atoms chemically bonded together
• Isotopes: atoms of the same element with different numbers of neutrons
• Mixtures: 2 or more elements or compounds that are not chemically combined together
• Separating mixtures

  Filtration: Insoluble solids and a liquid

  Crystallisation: Soluble solid from a solution

  Simple distillation: Solvent from a solution

  Fractional distillation: 2 liquids with similar boiling points

  Paper chromatography: Identify substances from a mixture
• First list of elements, Ordered, Gaps, Grouped, Metals and non metals, Problems

  Ordered: By atomic mass

  Gaps: No gaps

  Grouped: Not grouped

  Metals and non metals: No clear distinction

  Problems: Some elements not grouped right
• Mendeleev's periodic table, Ordered, Gaps, Grouped, Metals and non metals, Problems

  Ordered: Normally by atomic mass, some swapped around

  Gaps: Gaps for undiscovered elements

  Grouped: By chemical properties

  Metals and non metals: No clear distinction

  Problems: Incomplete
• Modern periodic table, Ordered, Gaps, Grouped, Metals and non metals, Problems

  Ordered: By atomic number

  Gaps: No gaps

  Grouped: By number of electrons in outer shells

  Metals and non metals: Metals to left, Non metals to right

  Problems: --
• Group 0

  Noble gasses

  Full outer shells

  Very unreactive (inert)

  Boiling points that increase down the group
• Group 1 elements

  Alkali metals

  React with oxygen, chlorine, and water
• Group 1 properties

  All have 1 electron in outer shell

  Very reactive as they only need to lose 1 electron to react

  Reactivity increases as you go down the group because

  • Atoms increase in side
  • Electrostatic attraction is weaker, easier to lose one outer electron

  Melting and boiling point decrease down group 1
• Group 7 elements

  Halogens

  Fluorine - F2 - Gas at room temp

  Chorine - Cl2 - Gas at room temp

  Bromine - Br2 - Liquid at room temp

  Iodine - I2 - Solid at room temp

  Melting and boiling point increase down group

  Reactivity decreased down group
• Group 7 reactivity

  Reactivity decreases down group 7 because

  • Atoms increase in size
  • Electrostatic attraction is weaker, harder to gain 1 electron
• Group 7 displacement

  More reactive group 7 elements can take the place of less reactive ones in a compound, this is called displacement