a) Identify the bond between H and F in HF molecule.

b) What property forms the basis of identification?

c) How does the property vary in periods and in groups?
 
a. The bond between H and F in the HF molecule is .
 
b. The property of forms the basis of identification.

c. Along the period, from left to right in the periodic table, the because of the increase in the , which attracts the electrons more strongly. On moving down a group, the of the elements decreases because of the increased number of energy levels.