In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?

Explanation

To determine which elements surrounding calcium (atomic number 20) in the Modern Periodic Table have physical and chemical properties resembling calcium, we will analyze the electronic configurations of the relevant elements. The elements in question have atomic numbers 12 (Magnesium), 19 (Potassium), 21 (Scandium), and 38 (Strontium).

### Step-by-Step Solution:

1. **Identify the Electronic Configuration of Calcium:**
- Calcium (Ca) has an atomic number of 20. Its electronic configuration is:
\[
\text{Ca: } 2, 8, 8, 2
...