The song is a Eurodance and dance-pop composition produced by the Norwegian duo Stargate, a marked departure from Diamandis' first album The Family Jewels.

Introduced to a glittering new nightlife, I fell in love with New York; it has this magic, fizzing white energy that no other city in the world has.

[3][4][2] Digital Spy editor Robert Copsey gave the song four out of five stars, regarding the chorus as "radio-friendly, synth-laden, and deeply hypnotic".

[2] In a review for MTV Buzzworthy, Bradley Stern opined that the song's "cutting, sinister lyricism and vocal acrobatics" separated it from Diamindis' previous work.

[4] Damien Ryan of So So Gay, rating the track four-and-a-half stars out of five, expressed it is "like nothing else we've heard from Marina, yet still manages to sound distinctly her".

[5] This Is Fake DIY's Gareth O'Malley scored "Radioactive" seven out of ten, concluding that "[t]his is a good pop song, yes, and an even better single, but she can definitely do better.

Following this, the couple is shown trashing a house, arriving at a motel, purchasing food from a supermarket, whilst in disguise, and sitting in a diner.