What is a group in the periodic table? In which part of a group would you separately expect the elements to have (i) the greatest metallic character (ii) the largest atomic size ? (b) In what respects do the properties of group 1 elements differ from those of group 17 elements? Explain with examples by taking one element from each group. (c) From the standpoint of atomic structure, what determines which element will be the first and which the last in a period of the periodic table? (d) Explain why, the properties of elements are repeated after 2, 8, 18 and 32 elements in the periodic table. What are the advantages of the periodic table?

Sodium has smaller size than chlorine and chlorine have larger atomic size Sodium is a metal and chlorine is non-metal.

Sodium is electropositive and chlorine is electronegative.

• The number of valence electrons in atom determines which element will be first and which is last in the periodic table.
• The electronic configuration are repeated because 2,8,18 and 32 are the maximum number of electrons than can be occupied by shells K, L, M and N. The properties are repeated because the electronic configurations are repeated.
• Advantages of periodic table

1. The study of elements and its properties clearly explained
2. By knowing the position of element in the periodic table, it becomes easy to predict the type of
3. An effective teaching aid for the students as well as teachers in schools and