Classification of Elements and Periodicity in Properties

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Modern Periodic Law: The physical and chemical properties of elements are periodic functions of their atomic numbers (Z), not atomic mass. Henry Moseley discovered this in 1913 by observing X-ray spec…

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Dobereiner's Law of Triads (1829): Elements arranged in groups of three showed a pattern where the middle element had properties intermediate to the other two, and its atomic weight was approximately …

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Mendeleev's bold decision to leave gaps in his 1905 Periodic Table demonstrated scientific insight and confidence. He predicted the existence of undiscovered elements (Eka-Aluminium/Gallium and Eka-Si…

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Step 1: Break 120 into digits: 1, 2, 0 Step 2: From Table 3.4, find root names: - 1 = 'un' (u) - 2 = 'bi' (b) - 0 = 'nil' (n) Step 3: Combine in order: un + bi + nil = unbinilium Step 4: Symbol uses f…

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Elements in the same vertical group have similar valence shell electronic configurations. Since chemical properties depend primarily on the number and arrangement of valence electrons, elements with i…

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The period number in the Periodic Table corresponds directly to the highest principal quantum number (n) of electrons in an element. Period 1 (n=1): Contains 2 elements (H, He) - 1s orbital filling. P…

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s-Block Elements: Groups 1 and 2 with valence configuration ns¹ and ns² respectively. Group 1 (Alkali Metals): Li, Na, K, Rb, Cs, Fr - highly reactive metals, lose one electron easily, form M+ ions. G…

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p-Block Elements: Groups 13-18 with valence configuration ns²np¹ to ns²np⁶. Include non-metals, metalloids, and poor metals. Range of Properties: (1) Non-metallic character increases left to right. (2…