Here's why:
* Electrons determine bonding: Electrons are the particles involved in chemical bonds. The way electrons are arranged around an atom's nucleus (its electron configuration) dictates how it will interact with other atoms to form molecules.
* Valence electrons: The electrons in the outermost shell of an atom, called valence electrons, are the ones most involved in chemical reactions. They determine an element's reactivity and how it will bond with other elements.
* Ionic and covalent bonds: The transfer or sharing of electrons between atoms results in ionic and covalent bonds, respectively. These bonds are the foundation of all chemical compounds.
While other particles like protons and neutrons contribute to an atom's overall identity (protons determine the element, and neutrons influence its isotopes), it is the behavior of electrons that ultimately governs the chemical properties of an element.
