2. Periodic Classification of Elements

Today, ______ elements are known to the scientific world. 16

118

______ made the first attempt to classify elements. 16

Dobereiner

Newlands fitted all the known elements in a table of _____ boxes. 17

56

Newland’s law of octaves was found to be applicable only upto ______. 17

Calcium

Eka-Aluminium is now known as ______. 19

Gallium

All the elements after ______ are man made. 22

Uranium

Atomic radius is expressed in the unit _____ . 25

Picometer

1 picometer = _____ meter. 25

10^{– 12}