What is the position of the element Z = 20 in the modern periodic table?

Options

A. `4^(th)` period
B. `3^(rd)` period
C. `2^(nd)` period
D. `1^(st)` period

Answer

To determine the position of the element with atomic number Z = 20 in the modern periodic table, we can follow these steps:

### Step 1: Determine the Electronic Configuration
The first step is to find the electronic configuration of the element with atomic number 20. The electronic configuration is determined by filling the orbitals in order of increasing energy levels.

- The filling order is as follows:
- 1s²
- 2s²
- 2p⁶
- 3s²
- 3p⁶
- 4s²

So, for Z = 20, the electronic configuration is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

### Step 2: Count the Electrons
Now, we can count the total number of electrons in the configuration:
- 1s² = 2 electrons
- 2s² = 2 electrons
- 2p⁶ = 6 electrons
- 3s² = 2 electrons
- 3p⁶ = 6 electrons
- 4s² = 2 electrons

Adding these gives us:
2 + 2 + 6 + 2 + 6 + 2 = 20 electrons

### Step 3: Identify the Valence Electrons
The valence electrons are the electrons in the outermost shell. In this case, the outermost shell is the 4th shell, which has:
- 4s² (2 electrons)

Thus, the number of valence electrons is 2.

### Step 4: Determine the Group Number
The group number can be identified based on the number of valence electrons. Since there are 2 valence electrons, the element belongs to Group 2.

### Step 5: Determine the Period Number
The period number is determined by the highest principal quantum number in the electronic configuration. Here, the highest principal quantum number is 4 (from the 4s²).

Thus, the element with atomic number 20 is in the 4th period.

### Conclusion
Based on the above analysis, the position of the element with atomic number Z = 20 in the modern periodic table is:
- **Group:** 2
- **Period:** 4

### Final Answer
The element Z = 20 is located in Group 2 and Period 4 of the modern periodic table.

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