Give the electronic configurations of the elements : `._(19)K, ._(25)Mn, ._(20)Ca`

Explanation

To find the electronic configurations of the elements Potassium (K), Manganese (Mn), and Calcium (Ca), we will follow the Aufbau principle, which states that electrons fill atomic orbitals in order of increasing energy levels.

### Step-by-Step Solution:

1. **Potassium (K, atomic number 19)**:
- The atomic number indicates that potassium has 19 electrons.
- We fill the orbitals in the following order:
- 1s: 2 electrons → 1s²
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