word - Mono-Tonic Crpytic-Clues

Answer for this puzzle is one word. All of the following clues have the same enumeration, but I am hiding it from you ;)

$500 note (?)
You ended up turning around (?)
Substance emitted through removing online games from personal profile (?)
Gas? Initially, no (?)
One brown liquid (?)
Uniform haiku ending (?)
A thousand missing leaders (?)

_{This puzzle is a part of Ooohh, it all makes sense now! :D}

Answer

The common enumeration is

(1)

and the answer is

DUBNIUM.

Details:

Roman numeral and musical note; (yo)U and U-turn; bromine and BIO minus .io; first letter of NO and nitrogen; I=iodine; phonetic alphabet and (haik)U; Roman numeral and first letter of MISSING.