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2: Atoms and Elements

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    393851
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    • 2.1: The Elements
      All matter is composed of elements. Chemical elements are represented by a one- or two-letter symbol.
    • 2.2: The Periodic Table
      The chemical elements are arranged in a chart called the periodic table. Some characteristics of the elements are related to their position on the periodic table.
    • 2.3: Atomic Theory and the Structure of Atoms
      Atoms are the ultimate building blocks of all matter. The modern atomic theory establishes the concepts of atoms and how they compose matter.
    • 2.4: Elements and Atomic Number
      Atoms are composed of three main subatomic particles: protons, neutrons, and electrons. Protons and neutrons are grouped together in the nucleus of an atom, while electrons orbit about the nucleus.
    • 2.5: Isotopes and Atomic Weight
      Elements can be identified by their atomic number and mass number. Isotopes are atoms of the same element that have different masses.  Atoms have a mass that is based largely on the number of protons and neutrons in their nucleus.
    • 2.6: The Quantum-Mechanical Model- Atoms with Orbitals
      Quantum mechanics involves the study of material at the atomic level. This field deals with probabilities since we cannot definitely locate a particle. Orbitals are mathematically derived regions of space with different probabilities of having an electron.
    • 2.7: Electron Configurations
      There are a set of general rules that are used to figure out the electron configuration of an atomic species: Aufbau Principle, Hund's Rule and the Pauli-Exclusion Principle.
    • 2.8: Electron Configurations and the Periodic Table
      The arrangement of electrons in atoms is responsible for the shape of the periodic table. Electron configurations can be predicted by the position of an atom on the periodic table.
    • 2.9: Valence Electrons
      Electrons are organized into shells and subshells about the nucleus of an atom.
    • 2.10: Periodic Trends - Atomic Size and Ionization Energy
      Certain properties—notably atomic radius, ionization energy, electron affinity and metallic character—can be qualitatively understood by the positions of the elements on the periodic table.


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