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Lecture 11_2025

The Periodic Table Overview

  • Understanding the arrangement and properties of the periodic table is crucial in chemistry.

Concentration

  • Concentration refers to the amount of substance in a given volume of solution.

  • Molarity (c) is defined as the number of moles of solute (n) per liter of solution (V).

    • Formula: c = n / V

    • Units: mol L⁻¹ or M

  • Amount in moles can be calculated using: n = m / M

    • Where m = mass and M = molar mass.

Learning Outcomes for the Periodic Table Lecture

  • Recognize relationships between elements in the same periods and groups.

  • Explain trends in atomic radii and ionization energies based on:

    • Effective nuclear charge.

    • Distance of the shell from the nucleus.

  • Predict properties of elements based on position in the periodic table, including:

    • Metallic, semi-metallic, or non-metallic characteristics.

    • Acid, basic, or amphoteric properties of oxides.

Structure of the Periodic Table

  • Periods: Rows that show changes in properties across.

  • Groups: Columns indicating elements with similar properties.

Historical Context

  • Dmitri Mendeleev created the first periodic table in 1869, arranging elements by properties.

Periodic Trends

  • The properties of elements are linked to their valence electron configuration.

    • Physical properties arise from valence electrons' attraction to the nucleus.

Ionization Energy (IE)

  • Defined as the energy required to remove an electron:

    Ionization Energy Equation

  • Trends:

    • Increases across a period due to the increasing effective nuclear charge.

    • Decreases down a group because of additional electron shells leading to increased shielding:

      • Vertical increase in shells leads to weaker attraction despite increased protons.

Atomic Radius

  • Defined as the distance from the nucleus to the outermost shell of electrons:

    • Trends:

      • Decreases across a period due to increasing nuclear charge pulling electrons closer.

      • Increases down a group due to additional electron shells.

Ionic Radius

  • Ionic vs Neutral Atom:

    • Cation: Smaller than neutral atom (lost outermost electrons).

    • Anion: Larger than neutral atom (gained electrons causing repulsion).

Electronegativity (EN)

  • Definition: Ability of an atom in a compound to attract bond electrons.

    • Calculated using effective nuclear charge and distance from nucleus:Electronegativity Equation

  • Pauling Scale:

    • Highest: Fluorine (4.0)

    • Lowest: Cesium (0.7)

Bonding and Electronegativity Trends

  • Bonding nature can be inferred from EN differences:

    • ΔEN < 2 → Covalent bonding

    • ΔEN > 2 → Ionic bonding

  • Increasing effective nuclear charge raises EN, while increasing radius decreases EN.

Learning Outcomes Recap

  • Recognize and explain trends in atomic structure and periodic properties, such as ionic and covalent bonding tendencies.

Questions for Further Review

  1. Compare physical and chemical characteristics of metals and non-metals in Group 14.

  2. Identify groups that may act as reducing agents.

  3. Rank atoms (Ca, Be, C, Br, Cs) by size.

  4. Identify the most electronegative element.