Question

Which all anomalous pairs of elements is not in medleevs table?

Answer 1

The major credit for a systematic classification of elements goes to Mandeleev. He has been trying to group the elements on the basis of some fundamental property of the atoms. When Mendeleev started his work, only 63 elements were known. He examined the relationship between atomic masses of the elements and their physical and chemical properties. Among chemical properties, Mendeleev concentrated mainly on the compound formed by elements with oxygen and hydrogen. he selected these two elements because these are very reactive and formed compound with most of the elements known at that time. The formulae of the compounds formed with these elements (i.e. oxides and hydrides) were regarded as one the basic properties of an element for its classification.