If 40 +1/2 the result is triple the number

Don't know exactly ans.

demerits of mendeleev's periodic table are : -

mendeleev 's periodic law table could not explain the position of the isotopes . according to periodic law , elements are arranged according to the order of their atomic mass , the isotopes should be given different places but as isotopes have the same chemical property , are placed in one place of the same group . mendeleev's periodic law could not explained the wrong order of atomic mass of cobalt and nickle . he could not able to explained the position of hydrogen placed with the alkali metals in group because like the alkali hydrogen reacts with chlorine,oxygen and sulphur to form compounds having the same general formula . since hydrogen has the same chemical properties with the alkali metals it is placed along with them .

i hope it