2024_SCC1123_Module5_2SPP (1)

Module Overview

  • Module Title: Chemical Bonding, Types of Solids and Intermolecular Forces

  • Handouts: None on CANVAS

  • Lab Activity: Experiment 5 – Maths skills for chemistry (Bring calculator)

  • Homework: Feedback Quiz 5 + OWL Questions

  • Text: SCC1123: Chemistry for the Life Sciences (2018)

Ionisation Energy

  • Definition: Energy required to remove an electron from an atom.

  • Formula: M(g) + energy  M+(g) + e-

  • 1st Ionisation Energy: Energy to remove the first electron.

  • 2nd Ionisation Energy: Energy to remove the second electron; significant increase when removing from a lower principal energy level.

  • Example: Magnesium (Mg)

    • 1st IE: 736 kJ/mol

    • 2nd IE: 1450 kJ/mol

    • 3rd IE: 7740 kJ/mol (indicates stability of Mg2+ ion configuration)

Electronegativity

  • Definition: Measure of an atom's ability to attract electrons.

  • Trend 1: Increases left to right across a period (groups V, VI, VII more electronegative).

  • Trend 2: Decreases down a group (more principal energy levels = less attraction to nucleus).

Types of Bonding

  • Bonding Types:

    • Metallic Bonding: Between metals (lattice of positive ions in a sea of electrons).

    • Ionic Bonding: Between metal and non-metal (transfer of electrons).

    • Covalent Bonding: Between non-metals (sharing of electrons).

Properties of Metallic Solids

  • Hardness: Variable, generally dense.

  • Melting & Boiling Points: High (5000C – 55000C).

  • Malleable & Ductile.

  • Conductivity: Good conductors in solid or liquid states.

Properties of Ionic Solids

  • Hard & Brittle.

  • Melting & Boiling Points: High (2000C – 20000C).

  • Solubility: Typically soluble in polar solvents.

  • Conductivity: Conduct only when molten or in solution.

Covalent Bonding

  • Definition: Sharing electrons between atoms.

  • Example Bonds:

    • Single (Cl-Cl), Double (O=O), Triple (N≡N).

  • Network Solids: Strong covalent bonds, e.g., diamond (C) and silicon dioxide (SiO2).

Properties of Covalent Network Solids

  • Extremely hard & brittle.

  • High melting & boiling points (1000C – 4000C).

  • Electrical non-conductors except graphite.

  • Insoluble in solvents.

Properties of Covalent Molecular Solids

  • Soft, waxy texture.

  • Low melting & boiling points (-200C – 1000C).

  • Non-conductors in all states.

  • Often soluble in non-polar solvents.

Intermolecular Forces

  • Types:

    • Dispersion Forces: Present in all molecules, weak, increases with molecular mass.

    • Dipole-Dipole Forces: Between polar molecules.

    • Ion-Dipole Forces: Between ions and polar molecules.

    • Hydrogen Bonds: Between H and F, O, or N.

  • Importance: Crucial in determining properties of substances.