ATOMIC STRUCTURE & PERIODIC TABLE

• What defines an element?


  All of the atoms in an element are the same
• What is the definition of a compound?


  A compound contains two or more different elements chemically combined in fixed proportions
• What does "fixed proportions" mean in the context of compounds?


  It means that the elements are combined in a specific ratio
• How do the properties of compounds compare to the elements they are made from?


  Compounds usually have totally different properties than the elements
• What is required to separate a compound back into its elements?

  A chemical reaction
• What characterizes a mixture?


  A mixture contains different elements or compounds that are not chemically combined
• What is a molecule in chemistry?


  A molecule has any elements chemically combined, even if they are the same element
• What are examples of compounds that are also molecules?


  Methane, water, and ammonia
• What elements are contained in methane?


  Carbon and hydrogen
• What elements are contained in water?


  Hydrogen and oxygen
• What elements are contained in ammonia?


  Nitrogen and hydrogen
• What distinguishes chlorine and oxygen molecules from compounds?


  Chlorine and oxygen molecules contain two atoms of the same element chemically combined
• Are chlorine and oxygen molecules considered compounds?


  No, they are not compounds
• What physical separation techniques can be used to separate mixtures?


  1. Filtration
  2. Distillation
  3. Crystallization
  4. Chromatography