In the modern periodic table, the element calcium (atomic number = 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these elements has physical and chemical properties resembling those of calcium and why?

Explanation

To determine which of the elements surrounding calcium (atomic number 20) has physical and chemical properties resembling those of calcium, we need to analyze the atomic numbers and their positions in the periodic table:

1. **Identify the Elements**: The elements surrounding calcium have atomic numbers 12 (Magnesium), 19 (Potassium), 21 (Scandium), and 38 (Strontium).

2. **Determine Groups and Periods**:
- Calcium (Ca) is in Group 2 (alkaline earth metals) and Period 4.
- Magnesium (Mg, atomic number 12) is in Group 2 and Period 3.
- Potassium (K, atomic number 19) is in Group 1 and Period 4.
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