Question

61. While developing the Periodic table, at few places Mendleev inverted the sequence of some
elements i.e. he placed an element with slightly greater atomic mass before the element of
lower atomic mass. Why did he do so?​

Answer 1

Answer:

While developing the Periodic Table, there were a few instances where Mendeleev had to place an element with a slightly greater atomic mass before an element with a slightly lower atomic mass. ... For example, cobalt (atomic mass 58.9) appeared before nickel (atomic mass 58.7)