- Why do we classify elements?
- What were the two criteria used by Mendeleev in creating his Periodic Table?
- Why did Mendeleev leave some gaps in his Periodic Table?
- In Mendeleev Periodic Table, why was there no mention of Nobel gases like Helium, Neon and Argon?
- Would you place the two isotopes of chlorine, Cl-35 and Cl-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.
1.We classify elements for making order of chaos and for understanding the properties of elements and compounds.
2.The two criteria used by Mendeleev in creating his Periodic Table are:
- Elements are arranged in the order of increasing atomic masses.
- Elements are also arranged according to the properties of their hydrides and oxides.
3.Mendeleev predicted the existence of some elements that had not been discovered in his time. Hence, he left some gaps in his Periodic Table to leave the scope for the search for the yet undiscovered elements.
4.Mendeleev did not mention nobel gases such as helium, neon and argon in his periodic table because they were still undiscovered in his time.
5.Though, Cl-35 and Cl-37 have different atomic masses, they should be placed in the same slot because their chemical properties are the same.