Element with electronic configuration as `[Ar]^(18)3d^(5)4s^(2)` is placed in `:`

Options

A. `1^(st)`group, `s-` block
B. `2^(nd) ` group, `s-` block
C. `5^(th) ` group, `d-` block
D. `7^(th) ` group, `d-` block

Explanation

To determine the placement of the element with the electronic configuration `[Ar] 3d^5 4s^2`, we can follow these steps:

### Step 1: Identify the Atomic Number
The electronic configuration starts with `[Ar]`, which corresponds to the atomic number 18 (the number of electrons in Argon). The additional electrons in the configuration are `3d^5` and `4s^2`.

**Hint:** Remember that the atomic number is the total number of electrons in a neutral atom.

### Step 2: Calculate the Total Number of Electrons
The total number of electrons can be calculated as follows:
- Electrons from Argon: 18
- Electrons from `3d^5`: 5
- Electrons from `4s^2`: 2

Total = 18 + 5 + 2 = 25

**Hint:** The total number of electrons corresponds to the atomic number of the element.

### Step 3: Identify the Element
The atomic number 25 corresponds to the element Manganese (Mn).

**Hint:** Use the periodic table to find the element corresponding to the atomic number.

### Step 4: Determine the Block and Group
The last electron in the configuration enters the `d` orbital, which indicates that this element is in the d-block of the periodic table.

To find the group number, we can use the formula:
- Group number = Number of valence electrons + Number of electrons in (n-1)d sub-shell

For Manganese:
- Valence electrons in `4s`: 2
- Electrons in `3d`: 5

So, Group number = 2 (from `4s`) + 5 (from `3d`) = 7

**Hint:** The group number can help you identify the chemical properties of the element.

### Step 5: Conclusion
The element with the electronic configuration `[Ar] 3d^5 4s^2` is Manganese (Mn), which is located in the d-block and belongs to group 7.

**Final Answer:** The element is placed in the d-block and is in group 7.

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