Give the advantages and defects of Mendeleev's
periodic table. Explain how modern periodic table is divide
into blocks. Also write general electronic configuration of
each block.
Answers
ADVANTAGES
1.MENDELEEV HAD PLACED FEW ELEMENTS WITH SLIGHTLY HIGHER ATOMIC MASS BEFORE ELEMENTS WITH SLIGHTLY LOWER ATOMIC MASS SO AS TO GROUP ELEMENTS OF SIMILAR CHEMICAL PROPERTIES TOGETHER.
2. MENDELEEV PREDICTED THE DISCOVERY OF SOME ELEMENTS THAT DIDN'T EXIST DURING HIS TIME. HE ALSO NAMED THEM BY PREFIXING THE SANSKRIT NUMERAL "EKA" TO THE NAME OF THE PRECEEDING ELEMENT IN THE SAME GROUP.
3.WHEN THE INERT GASES WERE DISCOVERED THEY COULD BE PLACES IN A SEPARATE GROUP WITHOUT DISTURBING THE EXISTING ORDER.
DEFECTS
1.MENDELEEV COULDN'T GIVE HYDROGEN A FIXED POSITION AS IT SHOWED SIMILARITY TO THE ALKALI METALS IN THE ELECTRONIC CONFIGURATION AND ALSO SHOWED SIMILARITY TO THE HALOGENS IN THEIR CHEMICAL PROPERTIES.
2.ISOTOPES OF DIFFERENT ELEMENTS HAVE DIFFERENT ATOMIC MASSES . MENDELEEV'S PERIODIC TABLE COULDN'T ACCOUNT FOR ISOTOPES.
3.IN MENDELEEV'S PERIODIC TABLE,ELEMENTS ARE NOT ARRANGED IN THE INCREASING ORDER ODF THEIR ATOMIC MASSES . THIS HAS PREVENTED THE DISCOVERY OF SOME ELEMENTS.