

Periods of modern periodic table are of 3 types: It contains 7 periods and are represented by n=one, n=two and so on. Periods: Modern periodic table contains horizontal rows called periods.All the groups are divided into sub groups A and B except 0 and VIII group in the modern periodic table.are kept in the 0 group at the extreme right side of the table. There are 7 periods and 18 groups in the table.The elements are arranged based on their increasing atomic number.The representative and transition elements have been separated.The groups of the table are divided into sub groups A and B due to their dissimilar properties, which make the study of elements specific and easier.However, the hydrogen is placed in group I A of the periodic table along with alkali metals due to its least atomic number which is '1'. The place of hydrogen in the periodic table has not yet been solved completely.Therefore, they find the same position in the periodic table. The isotopes of some element have the same atomic numbers.The wrong position of some elements like argon, potassium, cobalt and nickel due to atomic weights has been solved by arranging the elements in the order of increasing atomic number without changing their own places.Modern periodic table: The table, which is obtained after classifying elements based on modern periodic law, is called modern periodic table. Modern periodic law: It states, "All the physical and chemical properties of an element are the periodic functions of their increasing atomic number". Modern Periodic Table Henry Mosley's classification
