Humber Admissions Practice Test 2025 - Free Practice Questions and Study Guide for Humber College Admissions

Valence electrons are defined as the electrons found in the outermost energy level of an atom. This is significant because these electrons play a crucial role in determining how an atom interacts and bonds with other atoms. The number of valence electrons influences an element's chemical properties, including its reactivity and the types of bonds it can form.

In context, the electrons in the nucleus are actually protons and neutrons, which do not participate in chemical bonding. Electrons that are closest to the nucleus refer to those found in inner energy levels, which are not considered valence electrons. Additionally, while there may be electrons in the second shell of an atom, valence electrons are not confined to just the second shell; they can also reside in higher energy levels depending on the element.

Thus, the most accurate definition among the given options is those electrons residing in the outermost energy level, which are vital for the atom's chemical behavior and interactions.