Clearly identify each of the groups you are discussing
Compare and contrast the physical properties of the members of the group
Explain the physical properties of the group in terms of atomic structure and attractive forces between the particles
Identify, explain why and discuss how reactivity varies within the group 
Identify how, and explain why, reactivity varies as it does within each group
Throughout your discussions of the above characteristics draw pertinent comparisons between the two groups you have chosen to explore.