Final answer:
Chlorine and iodine have similar chemical properties because they are both halogens with seven valence electrons, leading to similar behaviors in chemical reactions such as forming ionic compounds with metals.
Step-by-step explanation:
The reason why elements such as chlorine (Cl) and iodine (I) have similar chemical properties is because they both belong to the same group in the periodic table known as the halogens. This group is characterized by elements that have seven valence electrons.
The chemical properties of elements within the same group are similar because they have the same number of valence electrons, which governs their tendency to lose, gain, or share electrons during chemical reactions.
For instance, when these halogens react with metals such as sodium (Na), they form ionic compounds like sodium chloride (NaCl) and sodium iodide (NaI), where the halogen atoms gain an electron to form negative ions (anions).
Another important consideration is the formation of ionic compounds, which involves a metal losing electrons to form positive ions (cations) and a nonmetal like chlorine or iodine gaining those electrons to achieve a filled valence shell.
This transfer of electrons results in the formation of compounds with vastly different properties from their constituent elements. An example is the reaction between sodium and chlorine to form sodium chloride, which is essential to life, whereas chlorine in its elemental form is poisonous.