The valence electrons of `._(29)Cu` lie in the

Options

A. K shell
B. M shell
C. N shell
D. both M and N shell

Explanation

To determine the location of the valence electrons of copper (Cu), we can follow these steps:

### Step 1: Identify the Atomic Number of Copper
The atomic number of copper (Cu) is 29. This means that a neutral copper atom has 29 electrons.

### Step 2: Write the Electron Configuration
The electron configuration of copper can be written as follows:
- The first two electrons fill the 1s orbital: 1s²
- The next two electrons fill the 2s orbital: 2s²
- The next six electrons fill the 2p orbital: 2p⁶
- The next two electrons fill the 3s orbital: 3s²
- The next six electrons fill the 3p orbital: 3p⁶
- The next ten electrons fill the 3d orbital: 3d¹⁰
- The last electron goes into the 4s orbital: 4s¹

Thus, the complete electron configuration of copper is:
\[ \text{Cu: } 1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^1 \]

### Step 3: Identify the Valence Electrons
Valence electrons are the electrons in the outermost shell (highest principal quantum number). In the case of copper, the outermost electrons are in the 3d and 4s orbitals.

From the electron configuration:
- The 3d subshell has 10 electrons (3d¹⁰).
- The 4s subshell has 1 electron (4s¹).

### Step 4: Determine the Principal Quantum Number
The principal quantum number (n) for the outermost shell (where the valence electrons are located) is 4, as the highest energy level in copper is 4 (from the 4s orbital).

### Conclusion
The valence electrons of copper (Cu) lie in the 4th shell (n=4).

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