Chemistry

• Ions


  Charged atoms formed when an electron is removed or added, changing the charge
• Cations


  • Usually formed when the outermost electron shell is mostly empty
  • Outer electrons are weakly bonded to the atom, making it easier for them to be lost
  • Most cations come from metal atoms
• Ionic compounds are hard because it takes a lot of force to break the bonds
• Ionic Compounds

  1. Cations and anions bond together, forming compounds made up of large crystal lattices

  2. Example: table salt, known as sodium chloride NaCl
• Ionic compounds have a high melting point because of the strong bond that holds them together, needing higher temperatures to break them
• Ionic compounds in solution can create a flow of electricity, making them good conductors of electricity
• Ions in solution

  1. Some ionic compounds are soluble in water, breaking the lattice apart when water molecules surround the anion and cation, separating them

  2. The ions are then dispersed within the water, known as being in solution

  3. They can be reformed (recrystallised) when the water is heated and evaporated away
• Anions

  • Occur when the outermost electron shell is almost full
  • The atom gains electrons until the shell is full
  • Almost all anions are non-metallic atoms
• Ionic bonding

  • Cations and anions are attracted to each other due to opposite electrical charges, forming an ionic bond
  • Ionic bonds holding crystal lattices together are usually strong
  • Ionic compounds are hard, brittle, and have high melting points
• Ionic compounds are brittle because the lattice does not bend, but shatters
• Ionic compounds in a solid state are not good conductors of electricity
• Types of Ions

  • Cations: formed when an atom loses one or more electrons, creating an ion with a positive charge
  • Anions: formed when an atom gains one or more electrons, creating an ion with a negative charge
• Atoms


  Electrically neutral because they contain an equal number of positive protons and negative electrons
• Bonding


  • A new chemical bond is formed when the outermost electrons of atoms interact and cause atoms to join together
  • A bond is a force that holds atoms together
  • The 3 main types of bonds are IONIC, COVALENT, and METALLIC
• Naming ions

  • Metal ions keep the name of the metal atom
  • Non-metal atoms form negative ions, changing the name to end in “ide”
  • Ions never occur alone in a substance, total positive charge equals total negative charge for neutrality
  • Ions have a charge due to unequal electrons and protons, called valency
• Covalent bonds

  • Form when 2 non-metal atoms share electrons to achieve full outer shells
  • Naming rules: Left side element named first, right side element named second ending in -ide, prefixes used to indicate
• Ionic bonds


  • Form when a metal with a nearly empty outer shell reacts with a non-metal with a nearly full outer shell
  • Example: Sodium Chloride (NaCl)
• Metallic bonds

  Metal atoms lose electrons to become positive ions, valence electrons are distributed throughout the lattice of positive metal ions
• Polyatomic ions


  Combination of several atoms to form an ion, formula must not be altered, brackets used when more than one polyatomic ion is needed
• Law of conservation of mass: In all chemical reactions, the number of atoms of each element involved must remain constant. Total mass of reactants equals total mass of products
• Writing correct chemical equations

  Write correct formula for each substance involved, balance the equation by adding coefficients to make sure it obeys the Law of conservation of mass