42 Lewis Dot Symbols and Lewis Structures (Writing Lewis Symbols for Atoms) (41/50) -- Introductory Chemistry

42 Lewis Dot Symbols and Lewis Structures (Writing Lewis Symbols for Atoms) LumenLearning Representing Valence Electrons in Lewis Symbols Lewis symbols use dots to visually represent the valence electrons of an atom. LEARNING OBJECTIVES Recall the Lewis structure formalism for representing valance electrons KEY TAKEAWAYS Key Points - Electrons exist outside of an atom ‘s nucleus and are found in principal energy levels that contain only up to a specific number of electrons. - The outermost principal energy level that contains electrons is called the valence level and contains valence electrons. - Lewis symbols are diagrams that show the number of valence electrons of a particular element with dots that represent lone pairs. - Lewis symbols do not visualize the electrons in the inner principal energy levels. Key Terms - principal energy levels: The different levels where electrons can be found and that occur at specific distances from the atom’s nucleus. Each level is associated with a particular energy value that electrons within it have. - valence level: The outermost principal energy level, which is the level furthest away from the nucleus that still contains electrons. - valence electrons: The electrons of atoms that participate in the formation of chemical bonds. - Lewis symbols: Symbols of the elements with their number of valence electrons represented as dots Lewis symbols (also known as Lewis dot diagrams or electron dot diagrams) are diagrams that represent the valence electrons of an atom. Lewis structures (also known as Lewis dot structures or electron dot structures) are diagrams that represent the valence electrons of atoms within a molecule. These Lewis symbols and Lewis structures help visualize the valence electrons of atoms and molecules, whether they exist as lone pairs or within bonds. Principal Energy Levels An atom consists of a positively charged nucleus and negatively charged electrons. The electrostatic attraction between them keeps electrons ‘bound’ to the nucleus so they stay within a certain distance of it. Careful investigations have shown that not all electrons within an atom have the same average position or energy. We say the electrons ‘reside’ in different principal energy levels, and these levels exist at different radii from the nucleus and have rules regarding how many electrons they can accommodate. As an example, a neutral atom of gold (Au) contains 79 protons in its nucleus and 79 electrons. The first principal energy level, which is the one closest to the nucleus, can hold a maximum of two electrons. The second principal energy level can have 8, the third can have 18, and so on, until all 79 electrons have been distributed. The outermost principal energy level is of great interest in chemistry because the electrons it holds are the furthest away from the nucleus, and therefore are the ones most loosely held by its attractive force; the larger the distance between two charged objects, the smaller the force the