A period on the periodic table refers to a horizontal row of elements. The periodic table is organized into rows (periods) and columns (groups or families). Each period corresponds to the highest energy level of electrons in the ground state of the elements within that row.
Key characteristics of periods include:
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Energy Levels: As you move from left to right across a period, the atomic number increases, indicating that electrons are being added to the same principal energy level.
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Physical and Chemical Properties: Elements in a period demonstrate a gradual change in properties—such as reactivity, metallic character, and electronegativity—as you move across from left to right.
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Number of Elements: The number of elements in each period varies, with the first period containing 2 elements, the second and third containing 8 elements each, the fourth and fifth holding 18 elements each, and the sixth and seventh periods containing 32 elements each (due to the inclusion of the f-block elements).
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Valence Electrons: The elements in a period have the same number of electron shells, but the number of valence electrons increases from left to right, influencing their chemical behavior.
In summary, periods are horizontal rows on the periodic table that exemplify trends in atomic structure and properties of the elements.
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