2: Atoms and Elements
- Page ID
- 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.