Modern Periodic Table


 
 
Concept Explanation
 

Modern Periodic Table

Modern periodic table: In 1913, Henry Moseley showed that the atomic number of an element is a more fundamental property and on the basis of this, he modified Mendeleev’s periodic law as “physical and chemical properties of the elements are a periodic function of their atomic number”. This is called modern periodic law. When the elements were arranged in the increasing order of the atomic number, the obtained table is called modern periodic law.

Features of Modern Periodic Table:

This table has 18 vertical columns, known as groups and 7 horizontal rows, known as periods.

Features of Groups:

  •   The groups are not divided into sub-groups.
  •   The elements present in a group have the same number of valence or similar electrons.
  •   The elements present in a group have the same valency.
  •   The number of shells increases as we go down the group.
  •   The elements present in a group have identical chemical properties.
  •   The physical properties of the elements such as melting point, boiling point, density in a group vary gradually.
  • Features of Periods:

  •  Elements of a period do not have the same number of valence electrons but they contain the same number of shells.
  • The number of valence shell electrons increases by one unit as the atomic number increases by one unit on moving from left to right in a period. Therefore, the atoms of different elements with same number of shells are placed in the same period.
  •  As the number of valence shell electrons changes, the chemical properties of the elements also change.
  •  Different periods have different number of electrons which can be explained on the basis of filling of electrons into various shells.
  • We can explain the number of elements in the periods based on how electrons are filled into various shells. Maximum number of electrons that can be accommodated in a shell is given by the formula, 2n^2.  Where, n = number of given shell from the nucleus.

  •   K-shell= 2 x (1)2 = 2, hence the first period has 2 elements and is called very short period.
  •   L-shell= 2 x (2)2 =8, hence the second period has 8 elements and is called short period.
  •   M-shell= 2 x (3)2 = 18 but the outermost shell can have only 8 electrons, so the third period also has only 8 elements thus, it is also called short period. Fourth and fifth periods have 18 elements and are called long periods.
  •   Sixth and seventh periods have 32 elements and are also called long periods.      
  • Some Facts:

    The identities of some elements included in the seventh period have not been fully established. It can also be regarded as an incomplete period.

    Block of Periodic Table:

    The periodic table is divided in four blocks:

  • 1. s-block elements: It includes group I (alkali metals) and group 2 (alkaline earth metals) elements.
  • 2.p-block elements: It includes group 13 to 18 elements.
  • 3.d-block elements: It includes group 3 to group 12. These are also called transition elements (in between s-block and p-block elements).
  • 4.f-block elements It includes 14 elements after lanthanum (La, 57), called lanthanoides and 14 elements after actinium (Ac, 89), called actinoides.
  • Chapters
    Pre-Historic Period
    Indus Valley Civilization
    Vedic Civilization
    Religious Reform Movement
    The Early Kingdoms
    The Mauryan Empire
    Post Mauryan Period
    The Age Of The Guptas
    Post Gupta Era
    Age of Rajput
    Khilji Dynasty
    Slave Dynasty
    Tughlaq and Sayyid Dynasty
    Vijaynagar Empire And Bahamani Kingdom
    Mughal Empire And Beyond
    Lodhi Dynasty
    Cholas, Chalukyas and Pallavas
    Arab Invasions
    Bhakti and Sufi Movement
    Rise of Sikhs, Jats and Marathas
    Administrative Structure of Delhi Sultanate
    Architecture During Medivial India
    Advent Of The Europeans
    Post Mughal Period
    Rise of New States in 18th Century
    Growth of British Paramountacy
    Socio Religious Reforms
    Constitutional Development of India
    Indian Struggle Against British Rule
    The Revolt Of 1857
    Education Under British Rule
    Role of Press in Freedom Struggle
    First Phase of National Movement
    Second Phase of National Movement
    Third Phase of National Movement
    Constitutional Development in India
    Constituent Assembly
    Union And Its Territory
    Structure of Indian Constitution
    Fundamental Rights and Duties
    The Union Executive
    The Union Legislature
    Constitutional Amendments and Provisions
    Judiciary In India
    Emergency Provisions
    Center - State Relations
    The State Executive
    The State Legislature
    Election Commission Of India
    Constitutional Organisation
    Non-Constitutional Organisation
    Local Self Goverment
    India - Size And Location
    Geological History Of India
    The Physical Features Of India
    Climate Of India
    Soils In India
    Natural Vegetation
    Windlife Conservation In India
    Drainage System of India
    Irrigation System Of India
    Agriculture In India
    Livestock And Fisheries In India
    Minerals And Energy Resources In India
    Means Of Transport In India
    Major Industries In India
    Tribes of India
    Census of India 2011
    Music
    Dance
    Theatre
    Pantings
    Art, Architecture & Culture of India
    Bio-Diversity
    Earth And Its Structure
    Land Rock And Soil
    Atmosphere, Climate And Weather
    Oceanography
    Human And Regional Geography
    Economic Growth And Development
    Sectors Of Indian Economy
    Economic Planning Of India
    Fiscal And Monetary Policy In India
    Infrastructure In India
    Effects Of British Rule On Indian Economy
    National Income
    Banking System In India
    Poverty And Unemployment
    Inflation And Trade Cycles
    Major Institutions
    Environmental Studies
    Tissues In Organism
    Cytology
    Classifucation Of Plants
    Structural Composition Of Plants
    Nutrition In Plants, Harmones And Plant Disease
    Ecosystem
    Classification In Animals
    Nutrition In Animals
    Human Digestive System
    Human Respiratory System
    Human Skeleton System
    Human Excretory System
    Human Nervous System
    Human Circulatory System
    Human Endocrine System
    Human Reproductive System
    Genetics
    Human Diseases
    States Of Matter
    Metals And Non Metals
    Acid Bases And Salts
    Element Compounds And Mixture
    Physical And Chemical Change
    Carbon And Its Compounds
    Periodic Classification
    Fuel, Combustion And Flame
    Environmental Chemistry
    Rest And Motion
    Work Power And Energy
    Gravitation
    Pressure And Its Effects
    Simple Harmonic Motion
    Sound and Waves
    Heat And Temperature
    Light - Reflection
    Electricity And Magnetism
    Modern Physics
    Science And Technology
    Force And The Laws Of Motion
    Light - Refraction
    Dispersion And Human Eye
    Magnetic Effect Of Electric Current
    Atom And Molecule
    Chemistry In Everyday Life
    Units And Dimensions
    Content / Category
    Class / Course
     
     


    Students / Parents Reviews [10]