Periodic table

• Precipitation reactions


  A reaction in which a new solid (product) is formed when two solutions (reactants) are mixed together
• Precipitate


  The new solid formed in a precipitation reaction

  
• Precipitation reactions must start with two solutions

  
• Solution


  An ionic compound that is soluble/dissolves in water and has become completely transparent
• Initial solutions


  • Made by dissolving solid ionic compounds (often known as salts) in water
  • Transparent (no solid or cloudiness but may have colour)
• Soluble


  When a substance dissolves in water
• The symbol (aq) is often placed at the bottom of a name/formula to show the ionic compound is soluble
• Not every ionic compound is soluble
• Solubility rules


  • Help us understand that the initial ionic compounds (reactants) will start as solutions
• Forming a precipitate - example 1

  1. Mix two solutions

  2. Depends on solubility of products

  3. Potassium nitrate is soluble, does not form precipitate

  4. Lead iodide is insoluble, forms solid precipitate

  
• Forming a precipitate - example 2


  1. Mix two solutions

  2. Depends on solubility of products

  3. Sodium nitrate is soluble, does not form precipitate

  4. Silver chloride is insoluble, forms solid precipitate

  
• Not all combinations of solutions will result in a precipitate
• Precipitation reactions


  A type of double displacement reaction where the two metal cations displace each other
• Representing precipitation reactions


  • Word equation with (aq) and (s)
  • Balanced equation using ionic formulas

  
• Periodic Table


  Arrangement of chemical elements based on their atomic number and chemical properties
• Atomic Number


  Number of protons in the nucleus of an atom
• In modern chemistry, the atomic number of an element matches the number of protons in the nucleus
• Periodic Table


  • Rows are called periods, columns are called groups
  • Elements in same group share similar chemical characteristics
  • Elements in same period have same number of electron orbitals
• Atomic Structure


  Models of the atom's structure
• Noble Gases


  Group 18 elements with full outer electron shells, so they are inert and not chemically reactive
• Noble Gases


  • Helium has 2 electrons in outer shell
  • Neon has 8 electrons in outer shell
• Types of Elements


  • Metals
  • Non-Metals
  • Metalloids
• Metals

  • Solid at room temperature (except mercury)
  • Can be polished to a shine
  • Good conductors of electricity and heat
  • Malleable and ductile
  • Usually melt at high temperatures
• Atoms


  • Too small to be seen with the naked eye
  • Too small for most scientific microscopes
• Elements


  Many identical atoms found together
• Non-Metals


  • Cannot be polished to a shine, usually dull or glassy
  • Brittle and cannot be bent
  • Poor conductors of electricity and heat
  • Usually melt at low temperatures
  • Many are gases at room temperature
• Atoms


  • May form into small groups
  • May form into large repetitive structures
• Metalloids


  Elements with some features of both metals and non-metals
• Parts of an atom


  • Positive(+) protons found in the nucleus
  • Negative(-) electrons orbiting the nucleus
  • Neutral(o) neutrons found in the nucleus

  
• Electrons


  Held to the atom by electrostatic (+/-) attraction
• Nucleus


  Small and dense, contains all the mass (electrons weigh virtually nothing)
• Atoms are largely empty space
• Atoms are always neutral overall
• Atomic number


  Atom/element's ID number, its unique
• Atomic number


  No. of (+)protons
• Since atoms are neutral, no. of (+)protons = no. of (-)electrons
• Mass number


  Often rounded to nearest whole number
• No. of (o)neutrons


  Mass number - no. of (+)protons
• The number of neutrons does not have to equal the number of protons/electrons
• Electron configuration


  Electrons exist in specific locations around the nucleus, called shells/energy levels