Discuss how electron affinity of elements changes along a period and down a group.

How will the tendency to lose electron change in a period?

What is screenig effect? How this effect acts on the elements across period and group?

How does the valency vary in going down a group?

What do you understand by electron affinity of an element ? Why electron affinity of chlorine is more than that of fluorine.

What is electronegativity of an element? How does electromegativity vary in a period and in a group in the periodic table?

Discuss how classification systems have undergone several changes over a period of time?

In the periodic table going down in fluorine group

How would the tendency to gain electrons change as you go from left to right across a period?

What is valency? How does it vary along the period?