Matter, Periodic/Chemical Trends, Chemical Bonding

• Empirical thinking: Comes from investigation and observation
• Theoretical thinking: Ideas created to explain observations
• Alchemists: Created gold from basic metal alloys
• Daltons Atomic Theory:

  1. All matter made of tiny, indivisible particle called atoms
  2. Atoms can not be created nor destroyed
  3. Chemical reactions occur when atoms rearrange themselves
  4. All atoms of ONE element are the same, atoms of DIFFERENT atoms are DIFFERENT
• Thompsons Model: "Blueberry muffin" --> Dough area of positively charged atom, blueberries are the negative electrons evenly dispersed in the atom
• What did Thompson use to discover his model of the atom?

  A Cathode ray tube --> Streamline of electrons which were attracted to a positive magnetic force
• Rutherford's Model: Discovered the nucleus --> contained positively charged particles called protons
• What did Rutherford use in his experiment?

  Gold foil--> Aimed positive alpha particles and saw that they deflected

  • Deflected by being repelled by a positive region of the atom and being attracted to nearby electrons
• Bohr's model: Energy levels--> Every atom has their own number of energy levels which contains different numbers of electrons
• Bohr's experiment: When atoms are excited (by extra energy) the release photons of specific wavelengths, depending on the electrons energy jumps.

  • Each element has their OWN line spectrum
• Energy levels closer to the nucleus are?

  Low energy levels
• Atomic number: The total number of protons (and thus electrons) of an element
• Atomic mass: Weighted AVERAGE of the all the existing isotopes for an element (Not whole number since it's an average)
• Mass number: The total number of protons and neutrons (Always whole number)
• Isotope: Alternate form of an atom (of an element) with different number of neutrons
• Flame Tests: Identifying elements based on the unique flame color they produce (Each element has a different flame since they have different # of electrons and energy levels)
• Octet rule: When combined elements tend to achieve eight electrons in their valence shell
• A mass spectroscope is used to?


  Identify isotopes and their percentage abundances
• Nuclear radiation: Energy or particles released when radioisotopes decay
• Radioisotopes: Unstable nuclei and releases radiation as a result
• Beta particles: Resemble electrons and can't penetrate aluminum
• Alpha particles: Resemble He nucleus (2 protons, 2 neutron), positive charge, can't penetrate paper
• Gamma rays: Electromagnetic rays, can't penetrate lead
• RAM formula: Percentage abundance isotope x isotope mass number
• Ionization energy: The amount of energy required to remove one valence electron from an atom
• Electron affinity: The amount of energy released when an atom gains a valence electron
• Atomic radius: The distance from an atoms nucleus to its outermost valence electron
• Effective nuclear charge: The net force acting on an electron by the nucleus
• Force is inversely proportional to distance
• What element has the highest ionization energy?


  Helium
• Would more or less energy be required to remove a SECOND electron from an atom?

  Way more energy --> Removing one electron increased the attractive force exerted on each electron
• Periodic Law: When elements are arranged in order of increasing atomic number, trends can be seen in their properties
• Reactivity increases... going down a group and R-L across period
• Elements in the same group have similar chemical properties (Since same number of valance electrons)