La (lanthanum) having atomic number 57 is a member of :

Options

A. s-block elements
B. p-block elements
C. d-block elements
D. f-block elements

Answer

To determine the block to which lanthanum (La) belongs, we will follow these steps:

### Step 1: Identify the Atomic Number
The atomic number of lanthanum (La) is 57.

### Step 2: Write the Electronic Configuration
To find the electronic configuration, we start with the atomic number and fill the electrons according to the Aufbau principle.

1. The nearest noble gas before lanthanum is xenon (Xe), which has an atomic number of 54.
2. Thus, we start with the electronic configuration of xenon:
- Xe: [Kr] 4s² 3d¹⁰ 4p⁶
3. After xenon, we need to add 3 more electrons to reach the atomic number of 57:
- 55: 6s² (2 electrons)
- 56: 4f¹ (1 electron)
- 57: 5d¹ (1 electron)

So, the complete electronic configuration of lanthanum is:
\[ \text{La: } [Xe] 6s^2 5d^1 \]

### Step 3: Determine the Block
The block of an element is determined by the subshell that contains the last electron. In the case of lanthanum, the last electron is in the 5d subshell.

### Conclusion
Since the last electron of lanthanum is in the d-orbital, lanthanum belongs to the **d-block** of the periodic table.

### Final Answer
La (lanthanum) belongs to the **d-block**.

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