which of the following is the incorrect match for atom of element?

Options

A. `[Ar]3d^(5)4s^(2) to 4^(th)"period",6^(th)` group
B. `[Kr]4d^(10) to 5^(th" period, "12^(th)` group
C. `[Rn]6d^(1) 7s^(2) to 7^(th)` period, 3th group
D. `[Xe]4f^(14)5d^(2)6s^(2) to `6th period, 4th group

Explanation

To solve the question of identifying the incorrect match for the atom of an element based on its period and group, we will analyze each option step by step.

### Step 1: Understand the Definitions
- **Period**: The period of an element is determined by the principal quantum number (n) of the outermost electron. It corresponds to the highest energy level that has electrons.
- **Group**: For d-block elements, the group number can be calculated as the sum of the electrons in the outermost s subshell (ns) and the d subshell (n-1)d.

### Step 2: Analyze Each Option

**Option 1**:
- Last electron enters the 4s subshell.
- **Period**: Since the last electron is in the 4s subshell, it belongs to the 4th period.
- **Group**: The number of electrons in the s subshell (2) plus the number of electrons in the d subshell (5, as it is a transition metal) gives us 2 + 5 = 7.
- **Conclusion**: This option states period 4 and group 7, which is correct.

**Option 2**:
- Last electron enters the 5s subshell.
- **Period**: The last electron is in the 5s subshell, so it belongs to the 5th period.
- **Group**: The number of electrons in the s subshell (2) plus the number of electrons in the d subshell (10) gives us 2 + 10 = 12.
- **Conclusion**: This option states period 5 and group 12, which is correct.

**Option 3**:
- Last electron enters the 6s subshell.
- **Period**: The last electron is in the 6s subshell, so it belongs to the 6th period.
- **Group**: The number of electrons in the s subshell (2) plus the number of electrons in the d subshell (3) gives us 2 + 3 = 5.
- **Conclusion**: This option states period 6 and group 5, which is correct.

**Option 4**:
- Last electron enters the 6s subshell.
- **Period**: The last electron is in the 6s subshell, so it belongs to the 6th period.
- **Group**: The number of electrons in the s subshell (2) plus the number of electrons in the d subshell (4) gives us 2 + 4 = 6.
- **Conclusion**: This option states period 6 and group 6, which is correct.

### Step 3: Identify the Incorrect Match
After analyzing all options, we find that:
- Option 1 is the only one that does not match the expected group number based on the electron configuration.

### Final Answer
The incorrect match for the atom of the element is **Option 1**.

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