THE ‘PERIODIC TABLE OF ELEMENTS’

About: 

• The periodic table of the chemical elements is a tabular display of the known chemical elements. 
  
  
• Salient Features: 
  • The elements are arranged by electron structure so that many chemical properties vary regularly across the table. Each element is listed by its atomic number and chemical symbol. 
    
    
  • Metals reside on the left side of the table, while non-metals reside on the right. 
    
    
  • The columns, called groups, contain elements with similar chemical behaviours. 
    
    
  
  
  
• Present status: 
  • The elements from atomic numbers 1 (hydrogen) through 118 (oganesson) have been discovered or synthesized, completing seven full rows of the periodic table. 
    
    
  • The first 94 elements all occur naturally. Elements 95 to 118 have only been synthesized in laboratories or nuclear reactors. 
    
    
  
  
  
• History: 
  • The ‘Periodic Table of Elements’ was written by Russian chemist Dmitri Ivanovich Mendeleev in 1869. 
    
    
  • Mendeleev’s finding was that “The elements, if arranged according to their atomic weights, exhibit an evident stepwise variation of properties”. 
    
    
  • While putting together all the 63 elements known at that time, his periodic table placed four slots between the known ones with question marks. 
    
    
  • The current periodic table is far removed from the original version of Mendeleev. Yet, the core principle that ‘properties of elements are periodic functions of the inherent properties of its atoms’ remain. 
    
    
  
  
  
• Significance: 
  • The periodic table is organized so scientists can quickly discern the properties of individual elements such as their mass, electron number, electron configuration and their unique chemical properties. 
    
    
  • Mendeleev’s profound impact on chemistry is comparable to those of his contemporaries, Gregor Mendel and Charles Darwin in genetics and evolution, respectively. For that reason, element 101 is aptly named as Mendelevium (Md).