Question

answer this please........​

Answer 1

Answer:

answer (a)

in modern periodic table the elements are arranged in increasing order of their atomic masses so all the isotopes have similar atomic mass so they are placed at same position....

answer (b) ....

in mendeleev table Cobalt and nickel are placed in a wrong order but in the modern periodic table which is based on atomic numberCobalt is placed before nickel because the atomic number of Cobalt is 27 and that of nickel is 28...