KCET2010Chemistrys Block Elements
For alkali metals, which one of the following trends is incorrect?
Options
- AHydration energy: Li > Na > K > Rb
- BIonization energy : Li > Na > K > Rb
- CDensity : Li < Na < K < Rb
- DAtomic size : Li < Na < K < Rb
Correct answer
C. Density : Li < Na < K < Rb
Step-by-step solution
In general, density increases on moving downward in a group but density of potassium (K) is lesser than that of the sodium (Na). This is because of the abnormal increase in atomic size on moving from Na (86 pm ) to K (227 pm ) . Thus, the correct order of density is Li < K < Na < Rb