Which one among the following is responsible for determining the chemical properties of an element?

The chemical properties of an element are primarily determined by its electrons, specifically those in the outermost shell known as valence electrons [1]. Chemical reactions involve the breaking and making of bonds between atoms, which occurs through the sharing, gaining, or losing of electrons to achieve a stable, completely filled valence shell configuration [3]. While the number of protons (atomic number) defines the identity of an element, it is the arrangement and number of electrons that dictate its reactivity, bonding behavior, and electronegativity. For instance, noble gases are chemically inert because they possess a full valence shell, whereas alkali metals are highly reactive due to having a single valence electron [2]. Neutrons do not influence chemical properties; isotopes of an element have different numbers of neutrons but exhibit identical chemical behavior because their electron configuration remains the same.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.1 BONDING IN CARBON – THE COVALENT BOND > p. 59
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.3 HOW DO METALS AND NON-METALS REA ALS REACT? > p. 46
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > 1.2 TYPES OF CHEMICAL REACTIONS > p. 6