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STRUCTURE OF ATOM - Coggle Diagram
STRUCTURE OF ATOM
Genesis of Periodic Classification
Dobereiner’s Triads → Groups of 3 elements, middle one has average atomic mass.
Newlands’ Law of Octaves → Every 8th element has similar properties.
Mendeleev’s Periodic Table → Based on atomic mass, predicted new elements.
Modern Periodic Law → Properties periodic function of atomic number.
Modern Periodic Table
18 Groups (vertical)
7 Periods (horizontal)
Features:
Elements arranged by atomic number.
Position linked to electronic configuration
Periodic Trends in Properties
Atomic Radius
Across period: Decreases (↑ nuclear charge).
Down group: Increases (↑ shells).
Ionic Radius
Cations < Atoms.
Anions > Atoms.
Ionization Enthalpy
Across period: Increases.
Down group: Decreases.
Affected by nuclear charge & shielding effect.
Electron Gain Enthalpy
Across period: Becomes more negative.
Down group: Becomes less negative.
Electronegativity
Across period: Increases.
Down group: Decreases.
Valency
Related to number of electrons in outer shell.
Chemical Reactivity
Metals: Reactivity increases down a group.
Non-metals: Reactivity decreases down a group.
Periodic Trends in Metallic/Non-Metallic Character
Across period: Metallic → Non-metallic.
Down group: Metallic character increases.
Anomalous Properties of Second Period Elements
Due to small size, high electronegativity, absence of d-orbitals.
Example: Diagonal relationship (Li–Mg, Be–Al).
Genesis of Periodic Classification
Dobereiner’s Triads – Average atomic mass rule.
Newlands’ Law of Octaves – Every 8th element similar.
Mendeleev’s Periodic Table – Based on atomic mass, left gaps, predicted new elements.
Modern Periodic Law – Properties are periodic function of atomic number.
Modern Periodic Table
Rows (Periods) – 7 (linked to shells).
Columns (Groups) – 18 (linked to valence electrons).
Blocks – s, p, d, f (based on orbital filled).
Nomenclature of Elements with Atomic Number > 100
IUPAC system: temporary names & symbols from Latin/Greek numerals.
Example: 110 → Un-un-nilium (Uun).
Electronic Configuration and Types of Elements
s-block: Groups 1 & 2 → Alkali & alkaline earth metals.
p-block: Groups 13–18 → Metals, nonmetals, metalloids.
d-block: Transition metals (Groups 3–12).
f-block: Inner transition metals → Lanthanoids & actinoids.
Periodicity of Properties
Due to recurrence of similar electronic configuration after regular intervals.
BY YUVASSREE