The periodic table is organized into periods and groups, which help categorize the elements based on their properties. Periods refer to the 7 horizontal rows of the table, starting from the far left. For instance, the first row includes hydrogen (H) and helium (He), marking it as Period 1. The second row, or Period 2, contains elements from lithium (Li) to neon (Ne). While there are currently 7 periods, the periodic table is dynamic; advancements in technology and exploration may lead to the discovery of new elements, potentially adding more rows in the future.
In contrast, groups are the vertical columns of the periodic table, also known as families or series. There are 18 groups, each containing elements that share similar chemical properties due to their electron arrangements. For example, Group 1, which includes hydrogen (H) down to francium (Fr), is known as the alkali metals, while Group 2, from beryllium (Be) to radium (Ra), is referred to as alkaline earth metals. Other notable groups include the nitrogen group (Group 15), the chalcogens (Group 16), and the halogens (Group 17). The noble gases, found in Group 18, were once called inert gases due to their perceived lack of reactivity, although some can form compounds under certain conditions.
Additionally, there are two special rows that are not part of the main table layout. The lanthanides, located below the main body of the table, follow lanthanum (La), while the actinides follow actinium (Ac). Understanding the structure of the periodic table, including the distinction between periods and groups, is essential for grasping the relationships and behaviors of different elements.