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Physical Science Study Guide: Unit 3 - Atomic Structure
1. Basic Concepts of Atomic Structure
- Atom: The smallest unit of an element, consisting of protons, neutrons, and electrons.
- Element: A pure substance made up of only one type of atom, defined by its number of protons (atomic number).
- Molecule: Two or more atoms bonded together. Can consist of the same or different elements.
2. Fundamental Particles
- Protons: Positively charged particles found in the nucleus. Number of protons = atomic number.
- Neutrons: Neutral particles found in the nucleus that contribute to atomic mass.
- Electrons: Negatively charged particles that orbit the nucleus in electron shells or energy levels. They are involved in chemical bonding.
3. Atomic Number and Mass Number
- Atomic Number (Z): The number of protons in an atom. Determines the element's identity.
- Mass Number (A): The total number of protons and neutrons in the nucleus.
- Calculation: Mass Number (A) = Number of Protons (Z) + Number of Neutrons (N)
4. Isotopes
- Definition: Atoms of the same element (same number of protons) that have different numbers of neutrons.
- Example: Carbon-12 (6 protons, 6 neutrons) and Carbon-14 (6 protons, 8 neutrons).
5. Electron Configuration
- Definition: The distribution of electrons in the atomic orbitals.
- Energy Levels: Electrons are arranged in energy levels around the nucleus. The first level can hold up to 2 electrons, the second can hold up to 8, and so on.
- Aufbau Principle: Electrons fill the lowest energy orbitals first.
- Hund's Rule: Every orbital in a given sublevel is singly occupied before any orbital is doubly occupied.
6. The Periodic Table
- Organization: Elements are arranged by increasing atomic number. Elements with similar properties are grouped together in columns (groups).
- Groups: Vertical columns in the periodic table that share similar chemical properties (e.g., alkali metals, noble gases).
- Periods: Horizontal rows that represent energy levels of electrons.
7. Atomic Models
- Dalton’s Model: Early model proposing atoms are solid spheres.
- Thomson’s Model: Introduced the "plum pudding" model, suggesting atoms are composed of positive matter with electrons scattered throughout.
- Rutherford’s Model: Proposed a dense nucleus surrounded by electrons based on his gold foil experiment.
- Bohr Model: Proposed electrons are in fixed orbits around the nucleus at specific energy levels.
- Quantum Mechanical Model: Current model that describes electron cloud probabilities rather than fixed paths.
8. Chemical Bonds
- Ionic Bonds: Formed when electrons are transferred from one atom to another, resulting in charged ions.
- Covalent Bonds: Formed when two atoms share electrons.
- Metallic Bonds: Formed by the attraction between positively charged metal ions and the sea of delocalized electrons.
9. Radioactivity
- Definition: The process by which unstable atomic nuclei lose energy by emitting radiation.
- Types:
- Alpha decay: Emission of alpha particles (2 protons, 2 neutrons).
- Beta decay: Conversion of a neutron into a proton (or vice versa), emitting beta particles.
- Gamma decay: Emission of gamma rays, high-energy photons.
10. Important Scientists and Contributions
- John Dalton: Proposed the atomic theory.
- J.J. Thomson: Discovered the electron and the concept of isotopes.
- Ernest Rutherford: Discovered the nucleus.
- Niels Bohr: Developed the Bohr model of the atom.
Study Tips
- Diagrams: Draw diagrams of atomic structures, including electron configurations and orbital filling.
- Flashcards: Create flashcards of key terms and concepts for quick review.
- Practice Problems: Work through problems involving the calculation of atomic and mass numbers, and electron configurations.
- Peer Discussion: Discuss these concepts with peers to reinforce understanding.
This guide summarizes the essential topics regarding atomic structure in physical science. Make sure to review your class notes and textbook for detailed explanations and additional context!
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