Valence Electrons and Periodic Table Insights

Oct 17, 2024

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Lecture Notes on Valence Electrons and Periodic Table

Understanding Valence Electrons

  • Bohr Model Review:
    • Electrons occupy energy levels or shells.
    • First shell holds 2 electrons; second and third hold 8.
    • Post-third shells are less consistent.
  • Valence Electrons: Electrons on the outermost shell.
    • Example:
      • Lithium has 1 valence electron.
      • Nitrogen has 5 valence electrons.
  • Valence vs. Valence Electrons:
    • Valence: Number of electrons needed to complete an outer shell.
    • Example: Lithium has a valence of 7 (needs 7 more electrons).
    • Example: Nitrogen has a valence of 3.

Structure of the Periodic Table

  • Periods (Rows): 7 periods.
  • Groups (Columns): 18 groups.
    • Handy mnemonic: G (group) resembles C for column; P (period) resembles R for row.
  • Lanthanides and Actinides: Rows 6 and 7 are at the bottom due to space constraints.
  • Synthetic Elements: After element 95, elements are man-made.

Types of Elements: Metals, Nonmetals, Metalloids

Metals

  • Properties:
    • Shiny, smooth, usually solid at room temperature (except mercury).
    • Good conductors of heat and electricity.
    • Typically cations, ductile, and malleable.
  • Examples: Iron, copper, aluminum.

Nonmetals

  • Properties:
    • Usually gases or brittle solids, poor conductors (insulators).
    • Tend to be anions.
  • Location on Periodic Table: Primarily on the right side.

Metalloids

  • Properties:
    • Exhibit properties of both metals and nonmetals.
    • Border the staircase on the periodic table.

Key Groups and Families

Alkali Metals (Group 1)

  • Characteristics:
    • Highly reactive, especially with water.
    • One valence electron.
    • Do not occur freely in nature.

Alkaline Earth Metals (Group 2)

  • Characteristics:
    • Reactive but less so than alkali metals.
    • Found in the Earth’s crust.

Transition Metals (Groups 3-12)

  • Characteristics:
    • Varying reactivity.
    • Includes common and industrial metals like iron, nickel, and titanium.

Post-Transition Metals

  • Characteristics:
    • Include metals like aluminum, tin, and lead.
    • Often located to the right of transition metals.

Halogens (Group 17)

  • Characteristics:
    • Highly reactive nonmetals, especially fluorine.
    • Diatomic molecules.

Noble Gases (Group 18)

  • Characteristics:
    • Inert, colorless, and odorless gases.
    • Full valence shell, non-reactive.
    • Used in lighting due to non-reactivity.

Chemical Bonding Concepts

  • Alkali Metals and Halogens form salts due to mutual electron exchange.
  • Noble gases are stable and non-reactive due to full electron shells.

Additional Concepts

  • Synthetic Elements: Elements post-95 are man-made.
  • Metalloids: Exhibit mixed properties, located along the staircase division.

These notes encompass key details and relationships between different groups of elements and their properties, helping to understand the periodic table's structure and applications.