If you're a non-metal liquid with 45 neutrons in your nucleus, you're most likely bromine (Br).

Here's why:

* Non-metal liquid: Bromine is a reddish-brown liquid at room temperature, making it one of only two non-metal elements that exist as liquids under standard conditions (the other being mercury).

* 45 neutrons: Bromine has two common isotopes, bromine-79 and bromine-81. Bromine-79 has 44 neutrons, while bromine-81 has 46 neutrons. The average number of neutrons in bromine is slightly over 45.

Therefore, based on the given information, it's highly probable that you're describing bromine.