Which soft metal in group 1 of the periodic table tarnishes within a few seconds of exposure to air?

Correct option is B

The correct answer is (b) Sodium.
 Sodium, which is a soft metal belonging to group 1 of the periodic table, tarnishes within a few seconds of exposure to air.
 This tarnishing occurs due to the formation of sodium oxide (Na2O) and sodium hydroxide (NaOH) on the surface of the metal when it reacts with oxygen and moisture in the air.
 As a result, the shiny surface of sodium quickly becomes dull and tarnished.
 The Group 1 elements are found in the s-block of the periodic table. Group 1 elements are also known as alkali metals.
 In an atom of ‘s’ block elements, the last electron enters ‘s’ orbital of the outermost orbit.