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1. Overall Structure of the Periodic Table (118 Elements)The periodic table officially recognized by IUPAC [IUPAC Periodic Table] consists of 118 chemical elements, organized into logical rows and columns:7 Periods (Horizontal rows): Indicate the number of electron shells in an atom.Periods 1, 2, 3: Short periods (fewer elements).Periods 4, 5, 6, 7: Long periods. Period 7 is the final period (ending with Oganesson - Og).18 Groups (Vertical columns): Groups of elements with similar valence electron configurations, resulting in similar chemical properties.Group A (Main groups, 1A to 8A): Comprise s-block and p-block elements.Group B (Transition groups, 1B to 8B): Comprise transition metals (d-block and f-block).2. Classification of Elements in the Periodic TableThe 118 elements are categorized into specific groups/families with distinctive characteristics:Group / FamilyPosition on the TableKey CharacteristicsExamplesAlkali MetalsGroup 1 (Except H)Very soft, highly reactive with water to form basesLithium (Li), Sodium (Na), Potassium (K)Alkaline Earth MetalsGroup 2Highly reactive, form basic oxidesMagnesium (Mg), Calcium (Ca), Barium (Ba)Transition MetalsGroup B blocks (3-12)Metallic luster, excellent conductors, multiple oxidation statesIron (Fe), Copper (Cu), Gold (Au)Lanthanides & Actinides2 separate rows at the bottomRare earth metals, many are radioactive elementsUranium (U), Plutonium (Pu)Nonmetals / MetalloidsTop right of Group APoor conductors, gain electrons during reactionsCarbon (C), Oxygen (O), Silicon (Si)HalogensGroup 17 (7A)Toxic, highly oxidizing, form saltsFluorine (F), Chlorine (Cl), Iodine (I)Noble GasesGroup 18 (8A)Chemically inert, stable electron configurationsHelium (He), Neon (Ne), Argon (Ar)3. Periodic Trends (Key Rules to Remember)When moving across or down the periodic table, keep these two core trends in mind:Across a Period (Left to Right):Metallic character decreases, nonmetallic character increases.Atomic radius decreases.Electronegativity increases.Down a Group A (Top to Bottom):Metallic character increases, nonmetallic character decreases.Atomic radius increases.Electronegativity decreases.
