The number of electrons present in the 4f-subshell of Gd (Z = 64) is

Explanation

To determine the number of electrons present in the 4f-subshell of Gadolinium (Gd, atomic number 64), we can follow these steps:

### Step 1: Understand the Position of Gadolinium
Gadolinium is a lanthanide element, which means it is part of the f-block of the periodic table. The f-block elements are characterized by the filling of f-orbitals.

**Hint:** Remember that lanthanides correspond to the filling of the 4f subshell.

### Step 2: Write the Electronic Configuration
To find the number of electrons in the 4f subshell, we first need to write the complete electronic configuration of Gadolinium. The atomic number of Gadolinium is 64, which means it has 64 electrons.

The electronic configuration of Gadolinium can be derived as follows:
1. Start with the noble gas preceding Gadolinium, which is Xenon (Xe, atomic number 54).
2. After Xenon, we fill the 4f subshell, followed by the 5d and 6s subshells.

The electronic configuration is:
\[ \text{Xe} \, 4f^7 \, 5d^1 \, 6s^2 \]

**Hint:** Use the Aufbau principle to fill the subshells in the order of increasing energy levels.

### Step 3: Count the Electrons in the 4f Subshell
From the electronic configuration \( 4f^7 \), we can see that there are 7 electrons in the 4f subshell.

**Hint:** The superscript indicates the number of electrons in that subshell.

### Conclusion
The number of electrons present in the 4f-subshell of Gadolinium (Gd) is **7**.

**Final Answer:** 7 electrons in the 4f subshell.