arranging the elements

• How many chemical elements have been isolated and identified?

  Over 100
• In what order are elements arranged on the periodic table?

  In order of increasing atomic number
• What does each element on the periodic table have compared to the preceding element?

  One proton more
• Why are elements arranged in columns on the periodic table?

  To group elements with similar properties
• What are the two main arrangements of the periodic table?

  • Vertical columns called groups
  • Horizontal rows called periods
• What do periods in the periodic table indicate?

  Number of electron shells an atom has
• How are periods numbered on the periodic table?

  From 1 to 7
• How many electron shells do elements in Period 2 have?

  Two electron shells
• How many outer electrons do Group 4 elements have?

  Four outer electrons
• What is the group number of an element indicative of?

  Number of valence electrons
• What is the exception to the group number rule regarding outer shell electrons?

  Helium has only two electrons
• How does the number of valence electrons influence an element?

  It influences how the element reacts
• How can we predict the reactions of elements in the same group?

  • Group number indicates valence electrons
  • Elements in the same group react similarly
  • Observing one element's reaction predicts others
• How does reactivity change among Group 1 metals?

  Increases as you move down the group
• How does reactivity change among Group 7 halides?

  Decreases as you move down the group