UNIT 1.2 BASIC IDEAS ABOUT ATOMS 2024

Overview of Atoms

  • Understanding the atom is essential for studying chemical reactions and radioactivity.

  • The model of the atom has evolved over time to better explain observations.

Mathematical Skills

  • Learners will develop skills such as:

    • Using ratios to solve half-life problems in radioactive decay.

    • Working with expressions in decimal and standard form, as well as using powers.

    • Changing the subject of equations and substituting values in energy calculations.

How Science Works

  • Learners should:

    • Use theories and models to develop scientific explanations.

    • Recognize that scientific knowledge develops over time.

    • Evaluate the applications and implications of science, including ethical considerations.

Key Learning Objectives

  • Learners should understand:

    • Radioactive decay and its effects on atomic number and mass.

    • Behavior and relative penetration of α, β, and γ radiation.

    • Concepts of half-life and its importance.

    • Risks posed by radioisotopes in various fields (health, medicine, industry).

    • Variation of first ionization energies and their relation to electronic structure.

    • Analysis of atomic orbitals, including shapes and occupancy order.

    • Origin and significance of emission and absorption spectra.

    • The energy-frequency relationship: E = hf (energy and frequency) and f = c/λ (frequency and wavelength).

    • Order of energy for infrared, visible, and ultraviolet light.

Key Terms

  • Atomic Number (Z): Number of protons in an atom.

  • Mass Number (A): Total of protons and neutrons in an atom.

  • Isotopes: Atoms with same protons but different neutrons.

  • Ion: Particle with unequal numbers of protons and electrons.

  • Alpha Particles (α): Positively charged helium nuclei (2 protons + 2 neutrons).

  • Beta Particles (β): Fast-moving electrons with negative charge.

  • Gamma Rays (γ): High-energy electromagnetic radiation, neutral.

  • Half-Life: Time required for half of a radioactive sample to decay.

  • Atomic Orbital: Region that can hold up to 2 electrons.

  • Electronic Configuration: Distribution of electrons in an atom.

  • Ionization Energy: Energy needed to remove an electron from an atom.

Structure of Matter

  • Sub-Atomic Particles:

    • Proton: Relative mass 1, charge +1, found in nucleus.

    • Neutron: Relative mass 1, charge 0, found in nucleus.

    • Electron: Very small mass, charge -1, found orbiting nucleus.

Isotopes

  • Isotopes have identical atomic numbers but differing mass numbers (e.g., carbon-12, carbon-13, carbon-14).

Formation of Ions

  • Formation occurs through loss or gain of electrons:

    • Loss = positive ions (cations).

    • Gain = negative ions (anions).

Radioactivity

  • Radioactive Decay: Unstable nuclei emit radiation to form new elements.

    • Alpha decay: Loss of 4 mass units and 2 atomic number units.

    • Beta decay: No change in mass but atomic number increases by one.

    • Gamma emission: No change in atomic properties; energy lost.

Penetrating Power of Radiation

  • Alpha: Stopped by paper.

  • Beta: Halted by aluminum.

  • Gamma: Requires concrete/lead for absorption.

Radiation Effects on Living Cells

  • Ionizing radiation can damage cells leading to catastrophic issues, including cancer.

  • Types of potential damage:

    • Acute effects: Rapid damage, possible cell death