Argon (Ar) Electron Configuration and Properties

Argon has 18 electrons. According to the Bohr-Bury scheme (2n² rule), these electrons are distributed in shells (K, L, M) as follows:

• K shell (n=1): 2 electrons
• L shell (n=2): 8 electrons
• M shell (n=3): 8 electrons

Shell Configuration: 2, 8, 8

The modern quantum mechanical model distributes the 18 electrons into subshells (s and p) in increasing order of energy levels (Aufbau principle):

1s² 2s² 2p⁶ 3s² 3p⁶

Breakdown:

• 1st energy level: 1s² (2 e⁻)
• 2nd energy level: 2s² + 2p⁶ (8 e⁻)
• 3rd energy level (Valence shell): 3s² + 3p⁶ (8 e⁻)

Argon's outermost shell (the 3rd shell) contains 8 electrons (3s² 3p⁶).

According to the Octet Rule, an atom with 8 electrons in its outermost shell is perfectly stable. Because its valence shell is completely full, Argon does not need to gain, lose, or share electrons with any other atom.

Therefore, the valency of Argon is 0 (zero). It is chemically inert, meaning it almost never forms compounds or reacts with other elements.

Because of its unreactive nature, Argon is used when an inert atmosphere is needed:

1. Incandescent light bulbs: Filled with argon to protect the hot tungsten filament from burning up (oxidizing).
2. Welding: Used as a shielding gas in arc welding to prevent the hot metal from reacting with oxygen in the air.
3. Document preservation: Historical documents (like the original US Declaration of Independence) are stored in sealed cases filled with argon gas to stop decay.