(a) In the modern Periodic Table, why does cobalt with higher atomic mass of 58.93 apear before nickel having lower atomic massof 58.71?
(c) Why could no fixed position be given to hydrogen in Mendeleev's periodic table?

In the modern periodic table, why does cobalt having higher atomic mass of 58.93 appear before nickel having atomic mass of 58.71?

No fixed position could be given to hydrogen in Mendeleev's Periodic table

What should be the position of Hydrogen in the Modern periodic Table?Why?

(a) Which two criteria did Mendeleev use to classify the elements in his periodic Table? (b) State Mendeleev's periodic law. ( c) Why could no fixed position be given to hydrogen in Mendeleev's Periodic Table ? (d) How and why does the atomic size vary as you go (i) from left to right along a period (ii) down a group ?

(i) In Mendeleev's Periodic Table, the elements were arranged in the increasing order of atomic masses. However, cobalt with atomic mass of 58.93 a.m.u. was placed before nickel having an atomic mass of 58.71 a.m.u. Give reason for the same. (ii) Write the formula of chlorides of Eka-silicon and Eka-aluminium, the elements predicted by Mendeleev.

(a) Which two criteria did Mendeleev use to classify the elements in his periodic table ? (b) State Mendeleev's periodic law. (c) Why is it not possible to give a fixed position to hydrogen in Mendeleev's periodic table ?

In Mendeleev's periodic table, the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give reason for the same.

In Mendeleev's periodic table, the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give reason for the same.

The Atomic number of an element is 35 where would you expect the position of this element in the periodic table ? Why ?

Position of element, having atomic number 25, in the modern periodic table.