1. Rearrange the columns 2 and 3 so as to match with the column 1.

Column I	Column 2	Column 3
i. Triad	a. Lightest and negatively charged particle in all the atoms.	1. Mendeleev
ii. Octave	b. Concentrated mass and positive charge.	2. Thomson
iii. Atomic Number	c. Average of the first and the third atomic mass	3. Newlands.
iv. Period	d. Properties of the eight element similar to the first.	4. Rutherford.
v. Nucleus	e. Positive charge on the nucleus.	5. Dobereiner
vi. Electron	f. Sequential change in molecular formulae	6. Moseley

Ans. (i – c – 5 ) , (ii – d – 3) , (iii – e – 6 ) , (iv – f – 1) , (v – b – 4), (vi - a – 2).