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Classification of Elements and Periodicity in Properties - Coggle Diagram
Classification of Elements and Periodicity in Properties
Early Attempts at Classification
Döbereiner’s Triads
Newlands’ Law of Octaves
Genesis of Periodic Classification
Dobereiner’s Triads → Group of 3 elements with similar properties
Newlands’ Law of Octaves → Every 8th element repeats properties
Mendeleev’s Periodic Law → Properties are periodic function of atomic masses
Left gaps for undiscovered elements (Eka-Aluminium, Eka-Silicon)
Predicted properties successfully
Limitations: wrong position of isotopes, anomalies, uncertain hydrogen position
Need for Classification
Large number of elements discovered → difficult to study individually
Systematic classification helps understand similarities, predict properties
Modern Periodic Law
Proposed by Moseley (1913)
Law → Properties of elements are periodic function of their atomic numbers
Basis → Electronic configuration
Modern Periodic Table (Long Form)
Periods → Horizontal rows (7 periods)
Groups → Vertical columns (18 groups)
Blocks → Based on last electron:
s-block (Groups 1, 2)
p-block (Groups 13–18)
d-block (Transition metals, Groups 3–12)
f-block (Inner transition – lanthanoids, actinoids)
Nomenclature of Elements (Z > 100)
IUPAC systematic naming (Unnilunium → Lawrencium, etc.)
Permanent names after confirmation
Electronic Configuration & Position in Periodic Table
Period number → Highest principal quantum number (n)
Group number → Valence shell configuration
Elements classified into s, p, d, f blocks
Types of Elements
s-block → Alkali & alkaline earth metals
p-block → Main group, includes metals, non-metals, metalloids, noble gases
d-block → Transition elements (variable oxidation states, coloured ions)
f-block → Inner transition (lanthanoids, actinoids, radioactive)
Metals, non-metals, and metalloids
Periodic Trends in Properties
Atomic radius → ↓ across a period, ↑ down a group
Ionic radius → Cations smaller, anions larger than parent atom
Ionization enthalpy → ↑ across a period, ↓ down a group
Electron gain enthalpy → Becomes more negative across period, less negative down group
Electronegativity → ↑ across a period, ↓ down a group
Periodicity in Chemical Properties
Valency/Oxidation state → Depends on electronic configuration
Anomalous behavior of 2nd period elements → Due to small size, high electronegativity, diagonal relationship
Periodic Trends & Reactivity
Reactivity of metals → increases down a group, decreases across a period
Reactivity of non-metals → decreases down a group, increases across a period
Oxides:
Left → basic oxides
Right → acidic oxides
BY YUVASSREE