General Chemistry: Chapter 2, Part 1

Lecture Objectives

• Define key terms related to the periodic table.
• Write chemical symbols for elements and isotopes.
• Calculate atomic weights from isotopic abundances.
• Differentiate between empirical and molecular formulas.

Introduction

• Over 114 elements known.
  • 83 stable and found in nature, though some are rare.
  • 7 radioactive elements found in nature.
  • 24+ elements not found naturally on Earth, some possibly in stars.

The Periodic Table

• Organizes elements based on properties.
• Contains a wealth of information critical to understanding physical world.
• Took centuries of research to develop.

Structure

• F block: Typically drawn below due to space constraints but belongs in the sequence.
• Blocks: Elements sorted by chemical properties (S, D, P blocks).
  • F block: Contains lanthanides and actinides.

Vocabulary

• Group: Each column with similar properties.
• Period: Each row.
• Atomic Number: Number assigned to each element, corresponds to position.
• Atomic Mass: Another number in elements' box, e.g., Hydrogen is 1.00794.

Groups to Memorize

• Alkali Metals: Group 1A
• Alkaline Earth Metals: Group 2A
• Halogens: Group 7A
• Noble Gases: Group 8A

Element Types

• Non-metals: Right side, blue-color in chart.
• Metals: Majority, large gray section.
• Metalloids: Straddle the line, highlighted in yellow.

Atoms

• Tiny, about 10^-10 meters in diameter.
• Number of atoms in small elements is huge (e.g., half-carat diamond has 5x10^21 carbon atoms).

Subatomic Particles

• Neutrons:

  • Located in nucleus.
  • No charge.
  • Mass: 1.00867 amu.

• Protons:

  • Also in nucleus.
  • Charge: +1.
  • Mass: 1.00728 amu.

• Electrons:

  • Orbit around nucleus.
  • Charge: -1.
  • Mass: Very small, often considered zero for calculations.

Fun Fact

• If atoms were 1 inch in diameter, you'd bump your head on the moon.