Question

How was morden perodic table was developed? write

Answer 1

In the modern periodic table, the elements are arranged according to their atomic number - not their relative atomic mass rows, called periods , in order of increasing atomic number.

vertical columns, called groups , where the elements have similar properties.

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Answer 2

$<p style="color: pink;font-family:cursive;background:blue;font-size:25px:">In 1869 Russian chemist Dimitri Mendeleev started the development of the periodic table, arranging chemical elements by atomic mass. He predicted the discovery of other elements, and left spaces open in his periodic table for them. In 1886 French physicist Antoine Bequerel first discovered radioactivity.$