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Chem1-_Unit_4.1_Subatomic_Particles__1_.key

Unit Overview

  • Unit 4: Going Nuclear!

  • Focus Areas: Subatomic particles, radioactivity, and nuclear chemistry.

Content Breakdown

Part I: Subatomic Particles

  • Brief History of Electricity

  • Discovery of Electrons, Protons, and Neutrons

  • Concepts of Isotopes and Ions

Part II: Nuclear Radioactivity

Part III: Nuclear Fission

Part IV: Nuclear Fusion

Learning Goals

  • Understand the discovery process of each subatomic particle.

  • Recognize the role each subatomic particle plays in atomic structure.

  • Utilize atomic symbols to describe atom composition.

  • Calculate average atomic mass from isotopic abundances.

  • Comprehend the significance and applications of various atomic models.

Essential Questions

  • How much empty space constitutes solid objects?

Atomic Models Development

  • Historical Context of Atomic Theories

    • Changed perceptions about atomic structure over time.

    • Key Models:

      • Solid Sphere Model (John Dalton, 1803): Indivisible particles.

      • Plum Pudding Model (J.J. Thomson, 1904): Electrons within a positive sphere.

      • Nuclear Model (Ernest Rutherford, 1911): Dense nucleus with electrons orbiting.

      • Planetary Model (Niels Bohr, 1913): Electrons in fixed orbits around the nucleus.

      • Quantum Model (Erwin Schrödinger, 1926): Electrons as wave functions in probabilistic clouds.

Brief History of Electricity

  • Early Observations

    • Electric eels and natural phenomena observed by ancient civilizations.

    • Thales of Miletus conduct experiments confusing static electricity with magnetism.

    • William Gilbert differentiates electricity and magnetism (1600s).

      • Named electricus from the Greek word for amber (electron).

  • Benjamin Franklin's Contributions:

    • Kite experiment linking lightning to electricity.

    • Developed lightning rods for safe electric discharge.

    • Identified two charge types: positive and negative, along with the law of conservation of charge.

Discovery of the Electron

  • JJ Thomson's Experiments:

    • Studied cathode rays leading to the identification of electrons as negative components of all elements.

    • Transition from indestructible models to the Plum Pudding model.

Discovery of the Nucleus and Protons

  • Rutherford's Gold Foil Experiment:

    • Revealed dense nuclei through scattering of alpha particles.

    • Concluded that positive charge was concentrated in the nucleus, leading to the discovery of protons.

    • Defined atomic number based on proton count.

Discovery of Neutrons

  • James Chadwick's Research:

    • Utilized radiation studies to discover neutrons, aiding in atomic mass understanding and nucleus stability.

  • Neutrons and protons exhibit strong nuclear force, acting as stabilizers in the nucleus.

Atomic Structure

  • Understanding Atom Composition:

    • Atoms are primarily empty space; electron clouds encompass their size.

    • Nucleus contains nearly all atomic mass; protons and neutrons significantly heavier than electrons.

    • Perception of solidity arises from electron repulsion, illustrating that solid matter is mostly empty space.

Isotopes and Ions

  • Defining Isotopes:

    • Same element differing in neutron number.

    • Mass number = total of protons and neutrons.

  • Calculating Atomic Mass:

    • Atomic masses on the periodic table represent weighted averages of isotopic abundances.

  • Ionic Charge Calculation:

    • In neutral atoms, protons = electrons; charge imbalance leads to ions (Li, Mg examples).

Summary of Atomic Models Evolution

  • From Dalton's indivisible spheres to Schrödinger's probabilistic clouds, the atomic model has evolved, reflecting advanced understanding of subatomic particles and interactions.