The periodic chart of the chemical elements, commonly known as the periodic table, groups atoms into families or groups based on their similar chemical properties and electronic configurations. While there are several ways to organize the elements, the most commonly used form of the periodic table arranges elements in groups of 18 vertical columns, also known as groups or families.
In this arrangement, there are indeed some groups that contain 3, 7, or 12 elements. Let's take a closer look at each of these cases:
Groups of 3: The group with three elements is typically found in the transition metals region of the periodic table. These elements exhibit similar chemical properties and share some common characteristics. Examples of such groups include Group 3 elements (Scandium, Yttrium, and Lanthanum) and Group 11 elements (Copper, Silver, and Gold).
Groups of 7: The group with seven elements is often seen in the halogens, a highly reactive nonmetallic group of elements. The halogens are located in Group 17 of the periodic table and include Fluorine, Chlorine, Bromine, Iodine, and Astatine. The seventh element in this group is sometimes occupied by the artificial element Tennessine (Ts).
Groups of 12: The group with twelve elements can refer to different groups depending on the context. One possible interpretation is the transition metal block, which consists of three series: 3d (Scandium to Zinc), 4d (Yttrium to Cadmium), and 5d (Lanthanum to Mercury). These series together make up twelve elements. Another interpretation could refer to the lanthanides and actinides, which are two series of elements located below the main body of the periodic table. Each series contains 15 elements, but if you exclude the f-block elements and consider only the elements shown in the main table, there are twelve elements in each series.
It's important to note that the grouping of elements into families on the periodic table is based on their chemical properties and electronic configurations rather than specific numbers like 3, 7, or 12. These numbers are a result of the way the periodic table is organized and are not fundamental to the properties of the elements themselves.