What will be the electronic configuration of an element with atomic number 19? 

2,8,8,1

The correct answer is option 3. 2,8,8,1.

Let us see the explanation:

1. Aufbau Principle:  According to the Aufbau principle, electrons occupy the lowest energy orbitals first before filling higher energy orbitals. This principle dictates the order in which electrons fill the electron orbitals within an atom.

2. Energy Levels and Sublevels:  In the electronic configuration, the numbers (such as 1, 2, 3) represent the principal energy levels or shells of the atom. Within each energy level, there are sublevels or orbitals (such as s, p, d, f), each with a different energy and capacity to hold electrons.

3. Filling Orbitals: Following the Aufbau principle, the electronic configuration of an atom with atomic number 19 (potassium) begins with filling the 1s orbital, which can hold a maximum of 2 electrons. Next, electrons fill the 2s and 2p orbitals, accommodating a total of 8 electrons. This corresponds to the electronic configuration \(2,8\) for the first two principal energy levels.

4. Valence Electrons: The valence electrons are the electrons in the outermost energy level of an atom. For potassium, which is in the third period of the periodic table, the outermost energy level is the third energy level. Therefore, we need to determine the configuration of the third energy level.

5. Filling the 3s Orbital:  The remaining 9 electrons for potassium are accommodated in the 3s and 3p orbital and 4s orbital. This completes the electronic configuration for potassium, which is \(2,8,8, 1\).

In summary, the electronic configuration \(2,8,8,1\) indicates that potassium has 2 electrons in the first energy level, 8 electrons in the second energy level, and 9 electrons in the third energy level. This configuration follows the principles of quantum mechanics and the Aufbau principle for filling electron orbitals in atoms.