SC3, SC4



John Dalton

  • All matter is made up of tiny particles called atoms
  • Atoms are tiny, hard spheres that can't be broken down into smaller parts
  • Atoms cannot be created or destoyed
  • Atoms in an element are identical

Atoms can be broken down into smaller parts

  • Atom - Smallest Particle
  • Element - Made of only one type of atom
  • Compound - Two or more different atoms that are chemically joined
  • Mixture - 2+ atoms not chemically joined
  • Molecule - Two or more atoms chemically joined
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                 Mass                   Charge

  • Proton         1                          +1
  • Neutron       1                           0
  • Electron   Neglible                    -1
  • These are subatomic particles
  • Every atom has atomic number and mass number
  • Atomic number = Number of protons in nucleus
  • Mass number = Number of protons and neutrons in nucleus
  • Outside of nuclues is made of shells of electrons and they fill the shell nearest the nucleus first then work outwards.
  • 1st shell holds max of 2 electrons
  • 2nd shell holds max of 8 electrons
  • 3rd shell holds max of 8 electrons
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  • Configuration - Distrubution of electrons around atom
  • Atomic number = Number of protons
  • Number or electrons = Number of protons
  • Number of neutrons = mass number - protons or mass number - atomic number
  • Isotopes - Atoms with same number of protons but not neutrons
  • Relative atomic mass  = (Number of isotope x Percentage in decimal format) + (Number of isotope x Percentage in decimal format).
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Elements / Periodic Table

  • Mendeleev arranged elements in order of increasing relative mass. He left gaps for the elements that weren't discovered yet
  • He swapped the positions of some elements if he thought their new postiton better suited their chemical properties.
  • Non metals are on the right
  • Metals are on the left
  • Horizontal rows are called periods - Increasing atomic number
  • Period tells you amount of shells
  • Number of electrons in outer shell = group number

6 = mass number

12 = Atomic number

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