Atomic structure + periodic table

• How were the first lists of elements ordered

  by atomic mass
• Why did Mendeleev leave gaps in his periodic table?


  To leave space for undiscovered elements
• How is the modern periodic table ordered, grouped, and how are the metals and non metals sorted?


  1. By atomic number
  2. By the number of electrons in the outer shells
  3. Metals to the left, non metals to the right
• Group 0 elements are called the noble gasses
• Noble gas properties:


  Full outer shells

  Very unreactive

  Boiling points increase as you go down
• What can group 1 elements react with?

  Oxygen, chlorine, and water
• General equations for alkali metals with oxygen, chlorine, and water


  Metal + oxygen -> metal oxide

  Metal + chlorine -> metal chloride

  Metal + water -> metal hydroxide + hydrogen
• Group 1 metals are called alkali metals
• Why does reactivity increase as you go down group 1?


  Bigger atoms

  Outer electron further away from the nucleus (more shells)

  Electrostatic attraction is weaker

  so it is easier to lose an electron
• Group 7 elements are called the halogens
• Halogens formula and state at room temp


  Fluorine = F2 = gas

  Chlorine = Cl2 = gas

  Bromine = Br2 = liquid

  Iodine = I2 = solid
• How does melting and boiling point change down group 7

  Increases as you go down
• How does reactivity change down group 7


  Decreases as you go down
• Why does group 7 reactivity decrease as you go down?


  Atoms are bigger

  Outer electron further away from the nucleus (more shells)

  Electrostatic forces of attraction are weaker

  so harder to gain an electron
• What is displacement 


  more reactive elements take the place of less reactive ones
• What is an atom?

  Smallest part of an element
• Daltons model of the atom

  Atoms as solid spheres that could not be divided into smaller parts
• What is the plum pudding model of the atom

  Sphere of positive charge with negative electrons embedded in
• Alpha scattering experiment

  Scientists fired alpha particles at a gold sheet only a few atoms thick, they expected it to just go through, but instead they found that some went through, but some were scattered, to explain this, the concluded that the positive charge and mass of an atom must be held in the centre (the nucleus)
• What did Niels Bohr discover

  Electrons orbit in fixed energy levels
• What did James Chadwick discover

  The neutron
• Where are protons and neutrons

  The nucleus
• Relative mass of sub-atomic particles

  Proton: 1

  Neutron: 1

  Electron: 0
• Relative charge of sub-atomic particles

  Proton: +1

  Neutron: 0

  Electron: -1
• How many electrons go in each shell

  2,8,8
• Element

  Substance made of one type of atom
• Compound

  Substance made of more than one type of atom chemically joined together
• Mixture

  Two or more substances not chemically combines
• Isotope

  Atoms of the same element with different numbers of protons