Reason for Using Argon in Arc Welding

Argon is a noble gas belonging to Group 18 of the periodic table, possessing a stable valence electron configuration of $ns^2 np^6$. Due to this filled octet, argon exhibits chemical inertness and extremely low reactivity under normal as well as high-temperature conditions.

During arc welding, very high temperatures are reached. At these elevated temperatures, metals readily react with oxygen, nitrogen, and moisture present in the air, forming oxides and nitrides that compromise the quality and strength of the weld joint.

Argon is used as a shielding gas in arc welding because:

1. It is chemically inert and has an extremely low reactivity with metals and other elements even at extremely high temperatures.
2. It displaces ambient atmospheric gases, creating a protective inert shield over the weld zone to prevent unwanted oxidation and contamination.

Thus, Argon is used in arc welding because of its low reactivity with metal.

Correct Option: (A)