Atom: The smallest unit of an element that retains the properties of that element, consisting of protons, neutrons, and electrons. Atomic Number (Z): The number of protons in the nucleus of an atom, w...Atom: The smallest unit of an element that retains the properties of that element, consisting of protons, neutrons, and electrons. Atomic Number (Z): The number of protons in the nucleus of an atom, which determines the element's identity. Valence Electrons: Electrons in the outermost shell of an atom, which determine the chemical properties and reactivity of the element.
