- How do we classify elements?
- What were the two criteria used by Mendeleev’s creating his periodic table?
- Why did Mendeleev leave some gaps in his Periodic Table?
- In Mendeleev’s Periodic Table, why was there no mention of noble gases like helium, neon and argon?
- Would you place the two isotopes of chlorine, C1-3S and Cl-37 in different slots because of their different atomic masses or in the same slot because of their chemical properties being same? Justify your answer.
We classify elements according to their properties and increasing atomic numbers so that we may obtain elements in regular order of their properties.
Atomic mass of the elements and similarity in physical and chemical properties of an element are the two criteria used by Mendeleev’s in creating his periodic table.
Mendeleev’s leave some gap in his periodic table because he believed that certain more elements existed but were not discovered till that lime.
Noble gases like helium, neon and argon were not discovered till that time.
Isotopes of chlorine, Cl-35 and Cl-37 have same atomic number and electronic configuration. So according to Modern periodic table we place them in same slot. Also due to same chemical properties of Cl-35 and Cl-37 they are placed in same slot.