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Atomic Number: | Atomic Mass: u
Calculate the number of moles from mass and molar mass.
Calculate the mass from moles and molar mass.
Calculate the number of electrons in an ion.
Calculate the wavelength from energy (λ = hc/E).
The periodic table exhibits several important trends in element properties:
| Property | Trend Left to Right | Trend Top to Bottom |
|---|---|---|
| Atomic Radius | Decreases (nuclei attraction increases) | Increases (more electron shells) |
| Electronegativity | Increases (more protons pull electrons) | Decreases (valence electrons further from nucleus) |
| Ionization Energy | Increases (harder to remove electrons) | Decreases (easier to remove distant electrons) |
| Metallic Character | Decreases (less willing to donate electrons) | Increases (more willing to donate electrons) |
Calculate solution concentration in chemistry
Find values using common physics equations
Convert between units for scientific calculations
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The periodic table is one of chemistry's most powerful organizational tools, arranging all known elements in a structured grid that reveals patterns in their properties. Created by Dmitri Mendeleev in 1869, the modern periodic table organizes elements by increasing atomic number (the number of protons in the nucleus) and groups them into columns (groups) with similar chemical properties and rows (periods) that share the same electron shell configuration. This arrangement allows scientists to predict element behavior, discover new elements, and understand fundamental chemical relationships.
Elements are categorized into several major groups, including metals (which comprise the majority of elements and generally conduct electricity and heat well), nonmetals (typically poor conductors with varied properties), and metalloids (elements with properties between metals and nonmetals). Further classifications include alkali metals, alkaline earth metals, transition metals, post-transition metals, lanthanides, actinides, halogens, and noble gases. Each group demonstrates characteristic behaviors and trends in reactivity, electronegativity, atomic radius, and other properties that follow predictable patterns across the table.
Beyond its descriptive power, the periodic table serves as an indispensable tool for modern scientific research, education, and industry. Researchers use it to predict chemical reactions and design new materials with specific properties. Engineers leverage elemental knowledge to develop everything from semiconductors to superalloys. Medical professionals rely on understanding elements and their compounds to create pharmaceuticals and diagnostic tools. The periodic table thus represents not just a catalog of elements, but a framework that continues to guide scientific discovery and technological innovation across disciplines.