atoms

• Atom


  • Too small to see
• Dalton (Snooker ball) model

  • Solid
  • Hard
  • No Charge
• Thomson Plum Pudding model


  • Electricity made of tiny, negatively charged particles (electrons)
  • These electrons (-) can be moved away from atoms so they must be on the outside
• Dalton and Thomson models


  Negative electrons stuck on the positive atom – balances charge
• Charge


  Positive or negative property of subatomic particles
• Rutherford's experiment


  1. Space

  2. All of the positive charge is at the centre of the atom (nucleus)

  3. Electrons orbit around the nucleus
• Subatomic particles


  • Proton
  • Neutron
  • Electron
• Protons


  • Subatomic particle located in the nucleus
  • Positive charge (+1)
  • The periodic table lists the elements in increasing number of protons (atomic number)
• Neutrons


  • Subatomic particle with no charge located in the nucleus
  • Helps keep the protons together in the nucleus
• Electrons


  • Small subatomic particles that orbit the nucleus of an atom
  • Fast moving, -1 negative charge, responsible for electricity flow
  • When the atom is neutral, the number of protons and electrons will be the same
• Atomic number


  Proton number
• Atomic mass


  Protons + Neutrons
• Subatomic particles and their characteristics

  • Protons: Positive charge (+1), located in nucleus
  • Neutrons: No charge, located in nucleus
  • Electrons: Negative charge (-1), orbit nucleus
• How to calculate proton, neutron and electron number

  1. Atomic number = Proton number

  2. Unless is an ion (charged) -> Proton number = Electron number

  3. Neutron number = Atomic mass – Proton number
• Atomic number = Proton number
• Unless is an ion (charged) -> Proton number = Electron number
• Neutron number = Atomic mass – Proton number
• Bohr model


  • Electrons travel around the Nucleus in shells
  • Electrons can have different amounts of energy
  • The amount of electrons in the outer shell tells us how the atom will react with other substances
• Octet rule


  • Predict the placement of electrons around the nucleus (electron orbitals)
  • The first shell (from inside out) can only fit 2 electrons
  • The second and third shell can fit 8 each
• Electron configuration of atoms

  • Lithium
  • Oxygen
  • Magnesium
• Mendeleev periodic table


  • Ordered elements by increasing atomic number
  • Predicted properties of undiscovered elements
• Groups


  Number of electrons in the outer shell (except Helium that has 2)
• Periods


  Number of shell (first, second, third..)
• Outer shell electron configuration

  Similar in each group, so similar properties
• Isotopes are atoms with the same number of protons but different number of neutrons
• Isotopes


  Importance in carbon dating
• Ionic, covalent and hydrogen bonding


  Different types of chemical bonding
• Parts of the periodic table

  • Groups
  • Periods
  • Metals
  • Non-metals
  • Metalloids
• Isotopes


  Atoms with the same number of protons but different number of neutrons
• 98.89% of carbon in nature is Carbon 12 (6 protons and 6 neutrons)
• 1.1 % is carbon 13 (6 protons and 7 neutrons)
• 1 carbon atom every trillion will be Carbon 14 (6 protons and 8 neutrons)
• Carbon 12, 13 and 14 are some of carbon isotopes. Isotopes explain why the atomic mass of elements in the periodic table have decimals. Other elements like hydrogen have isotopes too.
• Carbon 14 Dating


  Method for determining the age of organic material
• Ion


  A charged atom or molecule
• Atom or molecule becomes charged


  When it loses or gains one or more electrons
• Negative ion


  When an atom or molecule gains electrons (e.g. CL-)
• Positive ion


  When an atom or molecule loses electrons (e.g. Na+)
• Substances that break into ions when dissolved

  Like NaCl, where Cl takes an electron from Na to become Cl- and Na+
• Compound


  A substance that contains 2 or more different elements chemically combined