The term 'liquid ___ (refrigerant)' can be completed with the word 'NEON, ' which is a chemical element with the symbol Ne and atomic number 10. It is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. NEON is a noble gas that is used in many applications, including refrigeration. It is often used as a refrigerant because it has a low boiling point and is non-toxic.