short note structure of modern periodic table answer
Answers
features of modern periodic table:
This table has 18 vertical columns called groups and 7 horizontal rows known as periods.
A few important features of the elements present in groups are as follows:
1.The groups are not divided into subgroups.
2. The elements present in a group have the same number of valence or similar electrons.
3. The elements present in a group have the same valency.
4. The number of shells increase as we go down the group.
5. The elements present in a group have identical chemical properties.
6. The physical properties of the elements such as melting point ,boiling point, density in a group vary gradually.
Features of Periods:
1. Elements of a period do not have the same number of valence electrons but they contain the same number of shells.
2. The number of valence shell electrons increased by 1 unit as the atomic number increases by 1 unit on moving from left to right in a period.
3. As the number of valence shell electrons change is the chemical properties of the elements also change.
4. Different periods have different number of electrons which can be explained on the basis of filling of electrons into various shells.
Modern periodic table is based on the electronic configurations of elements in which Elements are arranged in the order of increasing atomic numbers in periods, and in groups the elements are placed having similar electronic configuration or having similar number of electrons in their outermost shells.