CUET Preparation Today
Case: Read the passage and answer the following questions The f-block consists of the two series, lanthanoids (the fourteen elements following lanthanum) and actinoids (the fourteen elements following actinium). . Because actinium closely resembles the actinoids, it is usually included in any discussion of the actinoids for which the general symbol An is often used. The chemistry of actinoids is complex. The complication arises partly owing to the occurrence of a wide range of oxidation states in these elements and partly because their radioactivity creates special problems in their study. |
| What is the main reason for greater number of oxidation states of actinoids than of lanthanides? |
More reactive nature of actinoids More energy difference between 5f and 6d than 4f and 5d Lesser energy difference between 5f and 6d than 4f and 5d None of the above |
| Lesser energy difference between 5f and 6d than 4f and 5d |
| Actinides exhibit larger oxidation states than lanthanides, because of the very small energy gap between 5f, 6d and 7s subshells. Thus, the outermost electrons get easily excited to the higher energy levels, giving variable oxidation states. |
