In which block will copper be placed if the Aufbau principle is not followed and the filling of electron takes place in the following sequence, `1s, 2s, 2p, 35, 3p, 3d, 4s, 4p, 4d, 4f...?` 

Options

A. s
B. p
C. d
D. f

Answer

To determine in which block copper will be placed if the Aufbau principle is not followed and the electron filling sequence is given as `1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f...`, we can follow these steps:

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

### Step 2: Fill the Electrons According to the Given Sequence
We will fill the electrons according to the specified sequence until we reach 29 electrons:

1. **1s**: 2 electrons → Total: 2
2. **2s**: 2 electrons → Total: 4
3. **2p**: 6 electrons → Total: 10
4. **3s**: 2 electrons → Total: 12
5. **3p**: 6 electrons → Total: 18
6. **3d**: 10 electrons → Total: 28
7. **4s**: 1 electron → Total: 29

### Step 3: Determine the Last Subshell Filled
From the filling sequence, we see that the last electron (the 29th electron) is placed in the **4s** subshell.

### Step 4: Identify the Block
The block in which an element is placed is determined by the subshell that receives the last electron. Since the last electron for copper is in the **s** subshell, copper will be placed in the **s-block**.

### Conclusion
Therefore, if the Aufbau principle is not followed and the filling of electrons occurs in the specified sequence, copper will be placed in the **s-block**.

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