The Periodic Table

• How are elements arranged in the periodic table?


  Elements are arranged in order of atomic (proton) number.
• What is the significance of groups in the periodic table?


  Elements with similar properties are found in the same columns, known as groups.
• What do elements in the same periodic group have in common?


  They have the same amount of electrons in their outer shell.
• Who ordered the periodic table by atomic weight?


  John Newlands ordered his table by atomic weight.
• What is the 'law of octaves' proposed by John Newlands?


  Similar properties occur every eighth element.
• What did Mendeleev do differently when ordering his periodic table?


  Mendeleev ordered his table by atomic mass but changed the order based on atomic weights in some places.
• What did Mendeleev leave gaps for in his periodic table?


  He left gaps for elements that he thought had not been discovered yet.
• Why is the table called a periodic table?


  Because similar properties occur at regular intervals.
• What is the significance of isotopes in the modern periodic table?


  Knowledge of isotopes explained why the order based on atomic weights was not always correct.
• How were elements ordered in the early 20th century?


  Elements were ordered in atomic (proton) number.
• What happens to the arrangement of elements when ordered by atomic number?


  All elements are placed in appropriate groups.
• What defines metals in the periodic table?


  Metals are elements that react to form positive ions.
• Where are metals typically found in the periodic table?


  Metals are found to the left and towards the bottom of the periodic table.
• What defines non-metals in the periodic table?


  Non-metals are elements that do not form positive ions.
• Where are non-metals typically found in the periodic table?


  Non-metals are found towards the right and top of the periodic table.
• What are the characteristic properties of alkali metals in Group 1?


  • Single electron in their outer shell
  • React vigorously with water to create an alkaline solution and hydrogen
  • React with oxygen to create an oxide
  • React with chlorine to form a white precipitate
  • Reactivity increases going down the group
• Describe the reactions of lithium, sodium, and potassium with water, oxygen, and chlorine.

  • Lithium:
  • Burns with a red flame, produces white solid
  • Fizzes steadily in water
  • Sodium:
  • Burns with an orange flame, produces white solid
  • Fizzes rapidly, melts into a ball
  • Potassium:
  • Produces a lilac flame, ignites with sparks
  • Reaction is more vigorous than sodium
• What is the electron configuration of noble gases in Group 0?


  • 8 electrons in their outer shell (except helium, which has 2)
  • Full outer shells
  • Unreactive due to stable arrangement of electrons
• What are the properties of halogens in Group 7?


  • Seven electrons in their outer shell
  • Exist as molecules made of pairs of atoms
  • React with metals to form ionic compounds with -1 charge
  • React with non-metals to form covalent compounds
  • Reactivity decreases down the group
• How does reactivity change among halogens as you go down the group?


  Reactivity decreases down the group due to increased electron shells.
• What happens when chlorine is bubbled through a solution of potassium bromide?


  Chlorine will displace bromine in the solution.
• What is the chemical equation for the reaction of chlorine with potassium bromide?


  Chlorine + Potassium Bromide → Potassium Chloride + Bromine
• What happens to the boiling points of noble gases as you go down the group?


  The boiling points increase with increasing relative atomic mass.
• Why do noble gases not easily form molecules?


  Because they have a stable arrangement of electrons with full outer shells.