No, atoms with the same atomic number (i.e., the same number of protons) do not necessarily have the same chemical properties. While the number of protons determines the element's identity, other factors influence an atom's chemical behavior. These factors include the arrangement of electrons, which determines the atom's electronic structure and its interactions with other atoms.
Chemical properties primarily depend on the atom's outermost electrons, known as valence electrons. Valence electrons are responsible for chemical bonding and reactions. Atoms with the same number of valence electrons tend to exhibit similar chemical properties. For example, all elements in Group 1 of the periodic table (e.g., hydrogen, lithium, sodium) have one valence electron and thus exhibit similar characteristics, such as reactivity and the tendency to lose that electron to form a +1 ion.
However, elements within the same group or period of the periodic table can have different chemical properties due to variations in their electron configurations. For instance, in the halogen group (Group 17), fluorine, chlorine, bromine, iodine, and astatine have the same number of valence electrons (7) but exhibit different reactivities due to variations in electron shielding and atomic size.
Additionally, isotopes of the same element have the same atomic number but different atomic masses. Isotopes may have slightly different chemical properties due to variations in their nuclear stability and reaction rates.
In summary, while the atomic number provides the elemental identity, other factors such as electron configuration, valence electrons, and isotopic composition influence an atom's chemical properties, leading to variations among atoms with the same atomic number.