Classification Of Elements And Periodicity In Properties

To determine which statement about lanthanoids is incorrect, let's analyze each option:

1. Lanthanoids are silvery white metals: This statement is correct. Lanthanoids, or lanthanides, are generally shiny and have a silvery-white metallic appearance.
2. Samarium shows +2 oxidation state: This statement is correct. Samarium does exhibit a +2 oxidation state, though it more commonly forms a +3 state.
3. Ce⁴⁺ solutions are oxidizing agents: This statement is correct. Cerium in the +4 oxidation state (Ce⁴⁺) is a well-known oxidizing agent due to its ability to be reduced to the more stable Ce³⁺ state.
4. Colour of lanthanoids is due to d-d transitions: This statement is incorrect. The color in lanthanoids arises due to f-f transitions, not d-d transitions, as lanthanoids have electrons filling their 4f orbitals. This is the incorrect statement as lanthanoids do not primarily involve d orbital electron transitions in their coloration.

Hence, the incorrect statement is: Colour of lanthanoids is due to d-d transitions.

In this question, we are tasked with identifying which of the given elements are metalloids. Let's first understand the characteristics and classification of metalloids in the periodic table.

Definition of Metalloids: Metalloids are elements that have properties intermediate between those of metals and non-metals. They are typically semiconductors, meaning they can conduct electricity better than non-metals but not as well as metals. This property is particularly useful in electronic devices.

Commonly Recognized Metalloids: Typically, the elements recognized as metalloids include Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), and sometimes Selenium (Se), depending on the classification.

Now, let's analyze the options provided:

1. Bi (Bismuth): Bismuth is a post-transition metal and is not classified as a metalloid.
2. Sb (Antimony): Antimony is a well-known metalloid. It exhibits properties that are intermediate between metals and non-metals. Thus, this is a correct choice.
3. P (Phosphorus): Phosphorus is a non-metal, not considered a metalloid.
4. Se (Selenium): Selenium is sometimes considered a metalloid, particularly in some scientific classifications, due to its properties, which include semiconductor behavior. Thus, this is also a correct choice.

Conclusion: Based on the above analysis, the elements given in the options that are classified as metalloids are:

Correct Answer: Antimony (Sb) and Selenium (Se).