Page 252 - Reliance Foundation School Koparkhairane - School Magazine - Zenith

atomic masses. The atomic mass of cobalt is slightly larger than that of

nickel, which would have placed them in backwards order if they had been
placed in the Periodic Table blindly according to atomic mass. Moseley's
experiments in X-ray spectroscopy showed directly that cobalt and nickel

have different atomic numbers, 27 and 28, and that they are placed in the
Periodic Table correctly by Moseley's objective measurements of their
atomic numbers.

Currently, we use the long form of the periodic table. It has 18 groups and 7

periods. The first period is the shortest period with two elements, the second
and third period is a short period

consisting of eight elements, the fourth and fifth are long periods with 18

elements and the sixth period is the longest period with 32 elements and the
seventh period is an incomplete period. Periodic table gives information
about physical and chemical trends like atomic radii, ionic sizes, physical
constants, density, reactivity, etc. It acts as a parameter for studying the
characteristics of various compounds.

The periodic table created by Mendeleev is a beacon for posterity and
continues to guide scientists and inspire them in their path of discovery of
new elements.

- Pratiksha Rajadhyaksha

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