perioodilistele

Perioodilistele, more commonly known as periodic tables, are tabular arrangements of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. This arrangement reveals trends in atomic radii, electronegativity, and ionization energy. The most widely used version is the standard periodic table, which depicts the elements in 18 columns, known as groups, and seven rows, known as periods.

The vertical columns, or groups, typically share similar chemical properties due to having the same number of valence electrons. Elements in the same group tend to react in similar ways. The horizontal rows, or periods, indicate the principal energy level of the outermost electrons. As you move across a period from left to right, atomic number increases by one, and the elements generally transition from metallic to nonmetallic character.

The periodic table is a fundamental tool in chemistry, providing a framework for understanding the behavior and relationships of the elements. It aids in predicting the properties of undiscovered elements and understanding the reactivity of known ones. Dmitri Mendeleev is widely credited with creating the first recognizable periodic table in 1869, arranging elements by atomic mass and leaving gaps for elements yet to be discovered, accurately predicting their properties. Later refinements, based on atomic number rather than atomic mass, led to the modern periodic table.