Final answer:
Valence electrons are those in the highest principal energy level of an atom and are key to determining an atom's chemical properties and reactivity. Atoms with a full valence shell are more stable and less reactive.
Step-by-step explanation:
The electrons in the atoms' outermost orbitals, which are generally associated with the highest energy principal energy level, are known as valence electrons. These electrons first fill the orbitals closest to the nucleus in a specific order, described by the Aufbau principle, which outlines that orbitals are filled from lower to higher energy levels. Valence electrons play a critical role in defining the atom's chemical properties, such as reactivity and the ability to form bonds.
Atoms with a full outermost energy level are more stable and exhibit lower chemical reactivity than those with incomplete valence electron shells. Conversely, atoms with unfilled valence shells are more likely to engage in chemical reactions to achieve a full outer shell, which generally increases their stability.
Using electron dot diagrams, we can visually represent the valence electrons and predict the atom's potential for participation in chemical reactions. In summary, understanding valence electrons is essential for grasping the behavior of atoms in various chemical contexts.