Two elements have set of quantum numbers of their last filled subshell of valence shell as follows:
`X to n = 4 , l = 1`
`Y to n = 5 , l = 2`
  Then which statement is incorrect? 

Options

A. Element Y has greater atomic number than atomic number of element X.
B. Element X has 10 electrons in d subshell.
C. Element X is not a transition element.
D. Atomic size of element Y is equal to the atomic size of element X.

Answer

To solve the question, we need to analyze the quantum numbers provided for the two elements, X and Y, and determine which statement about them is incorrect.

### Step 1: Identify the last filled subshell for each element
- For element X: The quantum numbers are n = 4 and l = 1.
- The azimuthal quantum number (l = 1) corresponds to the p subshell.
- Therefore, the last filled subshell for element X is 4p.

- For element Y: The quantum numbers are n = 5 and l = 2.
- The azimuthal quantum number (l = 2) corresponds to the d subshell.
- Therefore, the last filled subshell for element Y is 5d.

### Step 2: Determine the period and atomic number
- Element X (4p) belongs to the 4th period of the periodic table.
- Element Y (5d) belongs to the 5th period of the periodic table.
- Since elements in the 5th period have a higher atomic number than those in the 4th period, it is correct to say that element Y has a greater atomic number than element X.

### Step 3: Analyze the electron configuration
- Element X has its last filled subshell as 4p. The electron configuration before this would include 3s, 3p, and possibly 3d.
- Element Y has its last filled subshell as 5d. The electron configuration before this would include 4s, 4p, and 4d.

### Step 4: Evaluate the statements
1. **Statement about atomic number**: Element Y has a greater atomic number than element X. (This is correct.)
2. **Statement about electrons in D subshell**: Element X has 10 electrons in the D subshell. (This is incorrect because element X does not have a filled d subshell; it ends at 4p.)
3. **Statement about transition elements**: Element X is not a transition element. (This is correct since it is in the p-block.)
4. **Statement about atomic size**: The atomic size of element Y is equal to that of element X. (This is incorrect because atomic size increases down a group, so Y should be larger than X.)

### Conclusion
The incorrect statement is that "Element X has 10 electrons in the D subshell."

### Final Answer
The incorrect statement is: "Element X has 10 electrons in the D subshell."

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