The electronic configuration of an atom describes how its electrons are distributed among the various atomic orbitals. To determine the electronic configuration of Argon (Ar), we first need to know its atomic number.

Argon Atomic Number

Argon (Ar) is an element in the periodic table. Its atomic number (Z) is 18. The atomic number represents the number of protons in the nucleus of an atom. For a neutral atom, the number of electrons is equal to the number of protons. Therefore, a neutral Argon atom has 18 electrons.

Electron Filling Principles

To write the electronic configuration for these 18 electrons, we follow a set of rules and principles:

• Aufbau Principle: This principle states that electrons fill atomic orbitals in order of increasing energy level. Lower energy orbitals are filled before higher energy orbitals. The general order is $\text{1s} \to \text{2s} \to \text{2p} \to \text{3s} \to \text{3p} \to \text{4s} \to \text{3d}$, and so on.
• Pauli Exclusion Principle: This principle states that no two electrons in an atom can have the same set of four quantum numbers. Practically, this means that each atomic orbital can hold a maximum of two electrons, and these two electrons must have opposite spins.
• Hund's Rule of Maximum Multiplicity: This rule states that for degenerate orbitals (orbitals of the same energy, like the three p orbitals or five d orbitals), electrons will first occupy each orbital singly with parallel spins before any orbital is occupied by a second electron (paired up).

Step-by-Step Electronic Configuration of Argon

Let's distribute the 18 electrons of Argon into its atomic orbitals according to the principles mentioned:

1. 1s orbital: The lowest energy orbital is $\text{1s}$. It can hold up to 2 electrons.
   Remaining electrons: $18 - 2 = 16$
   Configuration so far: $\text{1s}^2$
2. 2s orbital: The next orbital in energy is $\text{2s}$. It can hold up to 2 electrons.
   Remaining electrons: $16 - 2 = 14$
   Configuration so far: $\text{1s}^2 \text{2s}^2$
3. 2p orbital: The $\text{2p}$ subshell consists of three degenerate $\text{2p}$ orbitals ($\text{2p}_x$, $\text{2p}_y$, $\text{2p}_z$). Each can hold 2 electrons, so the $\text{2p}$ subshell can hold a total of 6 electrons.
   Remaining electrons: $14 - 6 = 8$
   Configuration so far: $\text{1s}^2 \text{2s}^2 \text{2p}^6$
4. 3s orbital: After $\text{2p}$, the $\text{3s}$ orbital is next. It can hold up to 2 electrons.
   Remaining electrons: $8 - 2 = 6$
   Configuration so far: $\text{1s}^2 \text{2s}^2 \text{2p}^6 \text{3s}^2$
5. 3p orbital: Finally, the $\text{3p}$ subshell consists of three degenerate $\text{3p}$ orbitals. It can hold a total of 6 electrons. We have 6 electrons remaining, which perfectly fill this subshell.
   Remaining electrons: $6 - 6 = 0$
   Configuration so far: $\text{1s}^2 \text{2s}^2 \text{2p}^6 \text{3s}^2 \text{3p}^6$

Thus, the complete electronic configuration of Argon is $\text{1s}^2 \text{2s}^2 \text{2p}^6 \text{3s}^2 \text{3p}^6$.

Comparing with Options

Let's examine the provided options to find the correct electronic configuration for Argon:

Based on our step-by-step derivation, the electronic configuration $\text{1s}^2 \text{2s}^2 \text{2p}^6 \text{3s}^2 \text{3p}^6$ is the correct representation for Argon.