2: Atomic Structure
- Page ID
- 341886
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- 2.1: Atomic Structure
- Chemistry is based on the modern atomic theory, which states that all matter is composed of atoms. Atoms themselves are composed of protons, neutrons, and electrons. Each element has its own atomic number, which is equal to the number of protons in its nucleus. Isotopes of an element contain different numbers of neutrons. Elements are represented by an atomic symbol. The periodic table is a chart that organizes all the elements.
- 2.2: Masses of Atoms and Molecules
- The atomic mass unit (u) is a unit that describes the masses of individual atoms and molecules. The atomic mass is the weighted average of the masses of all isotopes of an element. The molecular mass is the sum of the masses of the atoms in a molecule.
- 2.3: Electron Configurations
- Electron configuration notation eliminates the boxes and arrows of orbital filling diagrams. Each occupied sublevel designation is written followed by a superscript that is the number of electrons in that sublevel.
- 2.4: Electronic Structure 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.
- 2.5: Periodic Trends- Atomic Size, Ionization Energy, Electron Affinity, and Metallic Character
- 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.