The periodic table organizes all elements by atomic number and reveals patterns in chemical properties. Understanding periodicity explains why element
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Why are noble gases unreactive?
Noble gases have filled valence shells with 8 electrons (except helium with 2). Atoms achieve stability with full valence shells, so noble gases do not need to gain, lose, or share electrons. This makes them unreactive.
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Why do atomic radii increase down a group but decrease across a period?
Going down a group adds new electron shells, increasing distance from the nucleus and thus atomic size. Going across a period keeps the same number of shells but adds protons, increasing nuclear charge and pulling electrons closer, decreasing size.
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What is electronegativity and why does it matter?
Electronegativity is the ability of an atom to attract electrons in a chemical bond. Elements with high electronegativity differences form ionic bonds, while similar electronegativities form covalent bonds. This determines the type of compound formed.
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