elements, compounds + mixtures

• How many different elements are there approximately?

  Around 100 different elements
• Where are the elements shown?

  In the periodic table
• What does each symbol in the periodic table represent?

  A different element
• What defines an element?

  All atoms are the same
• What is a compound?

  Two or more different elements chemically combined
• What does "fixed proportions" mean in a compound?

  Elements are combined in a specific ratio
• How do the properties of compounds compare to their constituent elements?

  Compounds usually have different properties
• What is the appearance of magnesium and sulfur?

  Magnesium is shiny metal; sulfur is yellow solid
• What do we need to do to separate a compound back into its elements?

  Use a chemical reaction
• What is a mixture?

  Different elements or compounds not chemically combined
• How can we separate a mixture?

  Using physical separation techniques
• What are some physical separation techniques?

  Filtration, distillation, crystallization, chromatography
• What is a molecule?

  Elements chemically combined, same or different
• What elements are contained in water?

  Hydrogen and oxygen
• Are chlorine and oxygen molecules or compounds?

  They are molecules but not compounds
• What is the composition of a chlorine molecule?

  Two chlorine atoms chemically combined
• What is the composition of an oxygen molecule?

  Two oxygen atoms chemically combined
• What are the key differences between elements, compounds, mixtures, and molecules?

  • Elements: Same atoms, represented by symbols
  • Compounds: Different elements chemically combined in fixed proportions
  • Mixtures: Different elements or compounds not chemically combined
  • Molecules: Any elements chemically combined, same or different
• What is the periodic table?

  • A table showing all known elements
  • Each element has a unique symbol
  • Elements are organized by atomic number
• what are compounds held together by

  chemical bonds
• how are bonds in a compound made

  by giving, taking or sharing electrons
• what does a compound of non-metals and metals consist of

  ions
• what does the opposite attraction of ions result in

  the ions being strongly attracted to each other which is called an ionic bonding
• what is it called when non-metals in a compound share electrons

  covalent bonding
• what is an isotope

  different forms of the same element which have the same number of protons but a different number of neutrons
• how do you calculate the relative atomic mass

  sum of isotope abundance × isotope mass number / sum of abundance of all isotopes