Phosphorus

Step 1: Reaction of phosphorus with nitric acid.
When phosphorus reacts with concentrated nitric acid, it gets oxidized to phosphoric acid ( ).

Step 2: Analyze the options.
- : This is phosphoric acid, which is formed when phosphorus is oxidized by concentrated nitric acid.
- : This is phosphorous acid, which is typically formed under milder oxidation conditions, not in this reaction.
- : This is pyrophosphoric acid, which does not form in this reaction.
- : This is hypophosphorous acid, also formed under different conditions of oxidation.

Step 3: Conclusion.
The correct answer is (1), , which is formed by the oxidation of phosphorus by concentrated nitric acid.

Step 1: Understanding the Concept:
Identify incorrect statements among the given options.
Step 2: Detailed Explanation:
(A) Incorrect - Ionisation energies do not always strictly increase from 3d to 5d in a simple manner.
(B) Correct - Cu (3d ) is diamagnetic; Cu (3d ) is paramagnetic.
(C) Correct - Ti shows colour due to d–d transition, while Sc is colourless.
(D) Incorrect - Transition elements can form complexes, so this statement is wrong.
Step 3: Final Answer:
Thus, incorrect statements are (A) and (D).

Concept: Reactivity depends on structure and strain

Step 1: White phosphorus has P tetrahedral structure.

Step 2: It has high angle strain (60 ).

Step 3: High strain makes it highly reactive.

Step 4: Other forms are more stable (polymeric).
Conclusion:
Most reactive = White phosphorus

Concept: White phosphorus exists as molecule with tetrahedral structure.

Step 1: Bonding.
Each phosphorus atom forms three bonds with other P atoms.

Step 2: Properties.

• Total lone pairs = 4 (one on each P atom)
• Bond angle =

Step 3: Conclusion.
Statement (A) is taken as false.