Lecture Notes: The Periodic Table

Overview

• The periodic table is a tool used to predict and construct chemical formulas.
• Key concepts include the differentiation between metals and non-metals, and the organization of elements in groups and periods.

Structure of the Periodic Table

• Groups/Families: Vertical columns (1-18) with similar properties.
• Periods: Horizontal rows with variable properties.
• Main Group Elements: Found in columns 1, 2, and 13-18.
• Transition Metals: Found in columns 3-12; have variable charges.
• Post-Transition Elements: Found in groups 13-15; about six elements not emphasized.

Types of Elements

• Alkali Metals: Soft, reactive metals forming +1 cations.
• Alkaline Earth Metals: Reactive metals forming +2 cations.
• Halogens: Gain electrons to form -1 anions.
• Noble Gases: Relatively unreactive, full electron shell, charge of zero.
• Metalloids: Elements touching the stair-step line (except aluminum), exhibit both metal and non-metal characteristics.

Important Trends and Charges

• Periodic Trend: Elements in the same group have similar charges.
• Charges by Group:
  • Group 1: +1
  • Group 2: +2
  • Group 13: +3
  • Group 15: -3
  • Group 16: -2
  • Group 17: -1

Noteworthy Elements

• Metals vs. Non-Metals: Separated by a diagonal black line starting with boron.
• Metalloids: Elements bordering the stair-step line, except aluminum.

Example Questions

• Halogen in the Fifth Period: Iodine
• Alkali or Alkaline Earth Metal in the Third Period: Magnesium
• Charge of Halogens: Generally -1 (anions)
• Metal Charges: Typically positive, as seen in their column numbers.

Applications

• This section prepares for writing chemical formulas using periodic trends, to be expanded in subsequent lectures.

---

• Tip: Annotate your periodic table with the stair-step line and charge indicators for groups to aid in understanding periodic trends in formulas.