Tiêu đề Chemistry 9th 2nd chapter-Eng.med@Textbooks All.pdf ✅

CHAPTER-2 PERIODIC TABLE merits of Mendeleev’s periodic table. Arranged in the order of increasing atomic mass. Systematic classification prediction of new elements correction of atomic mass demerits of Mendeleev’s periodic table not able to give a position for hydrogen position of lanthanides and actinides arranged the elements in the increasing order of atomic mass instead of atomic numbers. Modern periodic law The chemical and physical properties of elements are periodic functions of their atomic numbers. In the periodic table, the horizontal rows are called periods and the vertical columns are called groups.


The elements from group 3 upto group 12 are known as the transition elements. In d-block ,electrons are being added to the penultimate shell.