Chapter 7.1, Problem 3SSC

Interpretation Introduction

Interpretation:

The reason for all the elements of group 18 being unreactive when compared with those elements of group 17 which are all reactive needs to be explained.

Concept introduction:

Chemical compounds are formed when the atoms, ions or molecules of two substances are attracted towards each other forming a chemical bond. This bond can be electrostatic when two oppositely charged ions are attracted towards each other and this bond is said to be ionic bond. When there is sharing of electrons between the two molecules it is a covalent bond.

Answer to Problem 3SSC

The elements of group 18 are noble gases which have their outer energy levels complete and are therefore unreactive.

Explanation of Solution

The group 18 is located in the farther right side of the periodic table and is referred to as inert gases as their valence shells are completely filled. Due to filled shells, there are no free electrons for reaction to take place and hence are non-reactive. The elements are Helium, Neon, Argon, Krypton, Xenon and Radon.

The group 17 are located just before group 18 and has one electron less making it having electronic configuration as [noble gas] ns² np⁵. These groups are called as halogens which are fluorine, chlorine, bromine, iodine, astatine. As it needs one more electron to get octet electronic structure, it is very reactive.

Hence, group 18 elements are unreactive while group 17 elements are highly reactive.

Conclusion

The elements of group 18 are noble gases which have their outer energy levels complete and are therefore unreactive.