Which pair of elements has same chemical properties ?

Options

A. Z=13, Z=22
B. Z=3, Z=11
C. Z=4, Z=24
D. Z=2, Z=4

Answer

To determine which pair of elements has the same chemical properties, we need to identify elements that belong to the same group in the periodic table. Elements in the same group typically exhibit similar chemical properties due to having the same number of valence electrons.

### Step-by-Step Solution:

1. **Understand the Question**: We need to find a pair of elements that have the same chemical properties. This is typically true for elements in the same group of the periodic table.

2. **Analyze the Options**: We will examine each option provided to see if the elements belong to the same group.

- **Option 1**:
- Element with atomic number 13: Aluminum (Al)
- Electronic configuration: Ne 3s² 3p¹
- Group: 13 (p-block)
- Element with atomic number 22: Titanium (Ti)
- Electronic configuration: Ar 3d² 4s²
- Group: 4 (d-block)
- **Conclusion**: Different groups, so different chemical properties.

- **Option 2**:
- Element with atomic number 3: Lithium (Li)
- Electronic configuration: 1s² 2s¹
- Group: 1 (s-block)
- Element with atomic number 11: Sodium (Na)
- Electronic configuration: Ne 3s¹
- Group: 1 (s-block)
- **Conclusion**: Same group, so similar chemical properties.

- **Option 3**:
- Element with atomic number 4: Beryllium (Be)
- Electronic configuration: 1s² 2s²
- Group: 2 (s-block)
- Element with atomic number 24: Chromium (Cr)
- Electronic configuration: Ar 3d⁵ 4s¹
- Group: 6 (d-block)
- **Conclusion**: Different groups, so different chemical properties.

- **Option 4**:
- Element with atomic number 2: Helium (He)
- Electronic configuration: 1s²
- Group: 18 (noble gas)
- Element with atomic number 4: Beryllium (Be)
- Electronic configuration: 1s² 2s²
- Group: 2 (s-block)
- **Conclusion**: Different groups, so different chemical properties.

3. **Final Conclusion**: The only pair of elements that has the same chemical properties is found in **Option 2**: Lithium (Li) and Sodium (Na), as both belong to Group 1 of the periodic table.

### Answer:
**Option 2: Lithium (Li) and Sodium (Na)** have the same chemical properties.

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