Possible Clues:

• Gas forming 78% of the air
• Element in explosive information
• & 19 Down What elements of breathed air finally produce with one-to-one mixing?
• Element identified by Italian fellow endlessly in news
• A gas
• The majority of air
• Gas ring not working -- microwave finally employed
• C. 78% of the earth's atmosphere
• Gas put a tiny bit of taste into negroni cocktail
• Element with atomic number 7