Which of the following statements is not correct for the periodic classification of elements?

Options

A. The properties of elements are the periodic functions of their atomic number.
B. Non-metallic elements are less in number than metallic elements.
C. For transition elements,the last electron entres into(n-2)d-subshell.
D. None of these

Explanation

To determine which statement is not correct for the periodic classification of elements, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand the Modern Periodic Law**: The first statement claims that the properties of elements are a periodic function of their atomic number. According to the modern periodic law, this statement is indeed correct. The properties of elements do vary periodically with their atomic numbers.

**Hint**: Recall the modern periodic law which states that the properties of elements are periodic functions of their atomic numbers.

2. **Compare the Number of Non-Metals and Metals**: The second statement suggests that non-metallic elements are less in number than metallic elements. In the periodic table, there are significantly more metals (approximately 95) compared to non-metals (about 22). Therefore, this statement is also correct.

**Hint**: Count the number of metals and non-metals in the periodic table to verify this statement.

3. **Examine Transition Elements**: The third statement discusses transition elements and claims that the last electron enters into the n-2 d subshell. Transition elements are defined as those elements in which the last electron enters the d subshell. However, the last electron actually enters the (n-1) d subshell, not (n-2). Thus, this statement is incorrect.

**Hint**: Remember the electron configuration rules for transition metals and the definition of the d subshell.

4. **Conclusion**: After analyzing all the statements, we find that the third statement is incorrect. The correct statement should indicate that for transition elements, the last electron enters the (n-1) d subshell.

### Final Answer:
The incorrect statement is: "For transition elements, the last electron enters into n-2 d subshell."