CC3 & 4

• Particle


  The tiny pieces that all matter is made from.
• Atom


  The smallest independent particle. Everything is made of atoms.
• Size of atoms


  About 1 X 10^-10m in diameter.
• Dalton's model of atoms


  • Tiny hard spheres.
  • Can't be broken down.
  • Can't be created or destroyed.
  • Atoms of an element are identical.
  • Different elements have different atoms.
• Subatomic particles


  Smaller particles that atoms are made from.
• Proton


  Mass = 1

  Charge = +1

  Location = Nucleus
• Neutron


  Mass = 1

  Charge = 0

  Location = Nucleus
• Electron


  Mass = 1/1835 (negliable)

  Charge = -1

  Location = Shells orbiting nucleus
• Nucleus 


  Central part of an atom, 100,000 times smaller than the overall atom.
• Alpha particle


  Small positively charged particle made of two protons and two neutrons.
• Scattering


  When particles bounce back or charge direction.
• Rutherford's experiment

  Fired alpha particles at gold leaf, used a phosphor-coated screen to track where they went.
• Rutherford's results


  Most alpha particles went through, some scattered (charged direction).
• Rutherford's explanation


  Scattered particles hit a solid nucleus. Most did not hit it, therefore nucleus is small.
• Atomic number


  The bottom number on the periodic table, gives the number of protons and electrons.
• Atomic mass


  The top number on the periodic table, gives the total protons and neutrons together.
• Number of protons


  The atomic number.
• Number of electrons


  The atomic number.
• Number of neutrons

  Atomic mass - atomic number.
• Number of protons and electrons


  Equal, because each negative electron is attracted to a positive proton in the nucleus.
• Isotopes


  Atoms with the same number of protons but different number of neutrons.
• Describing isotopes


  Mass after the name (e.g. boron-10) or superscript mass before the symbol (^10B).
• Nuclear fission


  Large unstable atoms break into two smaller stable ones.
• Uses of fisson

  Nuclear power, nuclear weapons.
• Relative atomic mass, Ar


  The weighted average of the masses of all the isotopes of an element.
• Isotopic abundance 


  The percentage of an element that is made of a particular isotope.
• Calculating Ar


  • Multiply each mass by the decimal %.
  • Add these up.
  • Note: (decimal % = % / decimal)
• Dmitri Mendeleev


  Russian chemist, developed the periodic table.
• Mendeleev's periodic table


  Ordered by increasing Ar, some elements switched according to their properties.
• Chemical properties


  Includes reaction with acid and formula of oxide.
• Physical properties


  Includes melting point and density.
• Gaps in Mendeleev's periodic table


  Mendeleev left gaps where no known element fitted and predicted these would be filled with newly discovered elements.
• Eka-aluminium


  An element that Mendeleev thought would fill a gap. He predicted its properties, which matched gallium when discovered.
• Nobel gases


  Gases that do not react: He, Ne, Ar, Kr.
• Moseley's experiment


  Fired electrons at samples of elements and measured X-rays produced.
• Moseley's results


  Energy of x-rays produced proportional to the positive charge of the element.
• Conclusion from Moseley's work


  The atomic number must be the number of protons in the atoms.
• Pair reversals


  Elements (like Ar and K) that are not in order of increasing mass.
• Explaining pair reversals


  It means elements should be order elements by increasing atomic number instead.
• Shells


  Electrons orbit atoms in shells.