Models demonstrating electron shells or valence electrons are often shown two-dimensionally for simplicity and ease of representation. Here are a few reasons why two-dimensional representations are commonly used:
Simplification: Electron shells are typically represented as circular or elliptical orbits around the atomic nucleus. While this is a simplification of the actual three-dimensional nature of electron distribution, it provides a visual representation that is easier to understand and work with, especially for introductory purposes.
Planar symmetry: In many atoms, the electron shells and their associated subshells possess a certain degree of planar symmetry due to the spherical symmetry of the electron orbitals. Representing them in two dimensions helps illustrate this symmetry and allows for a clearer visualization of the electron distribution.
Mathematical convenience: In some cases, certain atomic properties and behaviors can be adequately described by considering electrons in a two-dimensional plane. This simplification allows for the use of mathematical models and calculations that are easier to handle, such as using orbital diagrams and electron configuration notations.
Teaching and learning purposes: Two-dimensional representations of electron shells are commonly used in educational settings to introduce and explain the concept of valence electrons, electron configurations, and chemical bonding. These simplified models help students grasp the basic principles and build a foundation of understanding before delving into more complex three-dimensional representations.
It's important to note that while two-dimensional representations are useful for conceptual understanding, they do not fully capture the true three-dimensional nature of electron distribution in atoms. Advanced models, such as quantum mechanical models, provide a more accurate depiction of electron behavior and spatial distribution but are mathematically and conceptually more complex to work with.