Cape Chemistry Study Guide Edited

• All matter is made up of tiny, indivisible particles called atoms
• Atoms can neither be created nor destroyed in a chemical reaction
• Atoms of a given element are identical in size, mass, and other properties, while atoms of different elements differ in such properties
• Atoms combine in simple whole-number ratios to form compounds
• In chemical reactions, atoms are combined, separated, or rearranged
• Same number of protons, but a different number of neutrons therefore different mass numbers
• A = Z + N

  Relationship between mass number, atomic number, and number of neutrons
• Relative atomic mass (RAM)


  The mass of one atom of the element relative to the mass of one atom of the carbon-12 isotope
• Relative isotopic mass


  The mass of an atom of a specific isotope of the element relative to the mass of the standard carbon-12 isotope
• A radioactive isotope has nuclei which undergo spontaneous disintegration producing electromagnetic radiation
• This decay is an attempt by the atom to attain nuclear stability
• The rate of decay of these nuclei is unaffected by chemical and physical processes and remains constant
• Half life


  The time taken for the amount or concentration of the isotope to fall to half its original value
• The shorter the half life, the greater the rate of decay and the more unstable the isotope is
• Causes of instability in nucleus: More protons than neutrons, More neutrons than protons, Too much protons and neutrons
• Electron capture


  Occurs in nuclei with an n/p ratio above the stable value, therefore it decreases the n/p ratio towards a stable value

  
• Alpha decay


  Occurs in isotopes which are unstable because their nuclei are too heavy
• If Z > 83, n/p > stable n/p, B-decay occurs
• If Z < 83, n/p < stable n/p, electron capture occurs
• If Z > 83, no stable isotopes, alpha decay/electron capture occurs
• When isotope have a n/p ratio below the stable value, the nucleus captures an electron from its innermost shell, this combines with a proton to form a neutron
• E = hv, v = c/λ, E = hc/λ

  Equations relating energy, frequency, wavelength, and the speed of light
• s, p, d and f

  Electron orbitals
• Dumbbell


  Shape of d-orbital
• Sphere


  Shape of s-orbital
• Cu - Copper, 29e

  Atomic number and electron configuration
• Cr - Chromium, 24e

  Atomic number and electron configuration
• The d-orbital of Chromium and Copper is half-filled and fully filled respectively and this will increase the stability of the atom
• As the distance increases

  The attraction of the positive nucleus for the negative electron decreases and the ionization energy decreases
• As the nuclear charge becomes more positive with increasing proton number


  Its attraction for the electrons increases and consequently the ionization energy increases
• Increasing atomic radii and shielding outweighs the increasing nuclear charge
• Electrons in the inner shells exert a repelling effect on electrons in the outermost shell of an atom, this is screening/shielding
• This screening effect means that effective nuclear charge is much less than the full positive charge in the nucleus
• Forces of attraction between states of matter

  • Ionic Bonds
  • Covalent Bonds
  • Hydrogen Bonds
  • Metallic Bonds
  • Van der Waal Forces
• All collisions are perfectly elastic and kinetic energy is conserved
• Gas molecules are in continuous random motion
• There are no intermolecular forces operating between the gas molecules
• Bond breaking
• Bond making
• Isotopes


  Same number of protons, but a different number of neutrons and different mass numbers