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1:Periodic Table Code


IkramUllah
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Periodic Table

The Periodic Table is a systematic arrangement of all known chemical elements, organized primarily by increasing atomic number (the number of protons in an atom's nucleus). It was first developed by Dmitri Mendeleev in 1869, who arranged elements based on their atomic masses and properties, leaving gaps for elements yet to be discovered. Today’s modern table is arranged in rows called periods (7 in total) and columns called groups or families (18 in total). Elements in the same group often share similar chemical behaviors because they have the same number of valence electrons. The table is divided into three main categories: metals, nonmetals, and metalloids. Metals, which make up the majority, are good conductors of heat and electricity and are found mostly on the left and center. Nonmetals are found on the right side and have diverse properties; many are gases or brittle solids. Metalloids have properties in between and form a stair-step line between metals and nonmetals. The middle block of the table (groups 3 to 12) contains the transition metals, which are known for forming colored compounds and having variable oxidation states. Group 1 elements are called alkali metals—very reactive, especially with water—while Group 2 are alkaline earth metals. Group 17 elements are the halogens, reactive nonmetals, and Group 18 are the noble gases, which are inert and stable due to full outer electron shells. At the bottom of the table, separated to keep the structure compact, are the lanthanides and actinides, which include rare earth elements and radioactive elements. The Periodic Table also reveals important trends across periods and down groups, such as atomic size, ionization energy, and electronegativity. These patterns help scientists predict the chemical behavior of elements and understand the structure of atoms. The table continues to grow as scientists discover and synthesize new elements, making it a living tool central to chemistry, physics, biology, and material sciences.