In the Periodic Table of Elements, the groups or families are designated by numbers. However, it's important to note that the group numbering can vary depending on the version of the periodic table being used. In the case of groups 8, 9, and 10, if we consider the 18-group system commonly used, they are referred to as Group 8, Group 9, and Group 10, respectively.
While it is true that these groups have the same number of valence electrons, which is 8, there are several properties that differentiate them:
Group 8 (Group VIII, sometimes called Group 18 or Group 0 in older systems): This group is known as the noble gases or inert gases. The noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These elements have a full outer electron shell with 8 valence electrons (except for helium, which has 2). As a result, noble gases are chemically stable and have very low reactivity. They are colorless, odorless gases at room temperature and are characterized by their low boiling points.
Group 9 (Group IX): Group 9 consists of the transition metal cobalt (Co) and its congeners. Transition metals have partially filled d-orbitals and exhibit a wide range of chemical properties. Cobalt is a hard, lustrous, silvery-gray metal with magnetic properties. It is used in various applications, including alloys, magnets, and industrial catalysts.
Group 10 (Group X): Group 10 includes the transition metal nickel (Ni) and its congeners. Nickel is a silvery-white metal with a high melting point. It is highly resistant to corrosion and is widely used in alloys, particularly stainless steel. Group 10 elements, including nickel, are known for their catalytic properties and are used in various industrial processes.
Although these groups have the same number of valence electrons, their positions within the periodic table, atomic structures, and chemical properties differ significantly. The grouping based on valence electrons alone does not fully capture the distinctions among elements within these groups.