CHEMISTRY

• Everything is made of atoms. Yes, even you.
• Atoms


  Consist of a core and some electrons. The core is made of protons and neutrons.
• Elements


  Different elements are determined by the number of protons
• Elements


  • Water (Hydrogen and Oxygen)
  • Sodium
• Quantum mechanics tells us that atoms do not actually look like the simple model, they look more complex
• Electron shells


  The electrons in the outermost shell are called "valence electrons"
• Most of chemistry is really just the behaviour of valence electrons
• Periodic table


  • Elements in the same column/group have the same number of valence electrons
  • Elements in the same row/period have the same number of electron shells
• Helium has 2 valence electrons, unlike the other noble gases which have 8
• Transition metals do not follow a simple pattern in the periodic table
• Elements with the same number of valence electrons


  Tend to show similar behaviour in chemical reactions
• Alkali metals


  • Have one valence electron
  • Are shiny metals
  • Are kind of soft
  • React in a certain way
• Isotopes


  Different isotopes of the same element have different numbers of neutrons in the core, most are unstable and radioactive
• Radioactive isotopes can be harmful and "will kill you"
• Charged atoms


  Atoms with more/less electrons than protons are called ions - negative ions are anions, positive ions are cations
• Information contained in the periodic table

  • Name and symbol of element
  • Number of protons in core (also number of electrons)
  • Atomic mass
• Categories in the periodic table

  • Metals (left of line)
  • Non-metals (mostly gases, right of line)
  • Semimetals (in between)
• Molecules


  Two or more atoms bonded together
• Compounds


  Molecules made of at least two different elements
• Compounds often behave completely differently than the elements they are made of
• Compounds


  • Table salt (sodium and chlorine)
• Molecular formula


  Represents the number of each atom in a molecule
• Isomers


  Molecules with the same molecular formula but different structures
• Lewis-Dot-Structure


  Represents the valence electrons and bonds of an atom
• Atoms bond to achieve a lower energy state, usually by filling their outer electron shell
• Covalent bond


  Sharing of electrons between atoms to achieve a full outer shell
• Electronegativity


  The strength of an atom's pull on shared electrons
• Ionic bond


  Forms when the difference in electronegativity is greater than 1.7, with one atom donating an electron to the other
• Ionic bond


  • Sodium and chlorine forming sodium chloride (table salt)
• Metallic bond


  Formed by a grid of positively charged nuclei surrounded by freely moving "delocalized" valence electrons
• Nonpolar covalent bond


  Electrons are shared equally between atoms
• Polar covalent bond


  One atom pulls on the shared electrons more strongly, creating a partial positive and negative charge
• Polar covalent bond


  • Water molecule, with oxygen partially negatively charged and hydrogens partially positively charged
• Electric dipole


  A molecule with a partial positive and negative charge
• Intermolecular forces (IMFs)


  Forces acting between polar molecules or atoms
• Hydrogen bond


  A strong IMF that forms when hydrogen is bonded to a highly electronegative atom like oxygen, fluorine or nitrogen
• Solvent


  A polar substance like water that can dissolve other polar and ionic substances by interacting with their charges
• Water is an excellent solvent due to its polarity, but cannot dissolve nonpolar substances like oil
• Van der Waals forces

  Temporary dipoles that form between nonpolar molecules due to the movement of electrons
• Surfactants


  Molecules with a polar "head" and nonpolar "tail" that can surround and transport nonpolar substances in water