Question

1. Which is the element among alkali metals having lowest ionization enthalpy? 

2. What is meant by valence of an element? How it varies in the periodic table? 

3. 

Identify the elements A, B, C and D, if the graph represents halogens.

Answer 1

1. Fr 

2. Valence of an element is the combining capacity of that element. In the case of representative elements the number of valence electrons increases from 1 to 8 on moving across a period, the valence to the element with respect to H and Cl increases from 1 to 4 and then decreases from 4 to zero. On moving down a group, the number of valence electrons remains same and, therefore, all the elements in a group exhibit same valence. 

3. A = F, B = Cl, C = Br, D = I