Original Arc Reactor – Iron Man – some time after his work during World War II, Howard Stark began studying the Tesseract and eventually developed an idea for a new power source that would be able to supply clean energy on a large-scale. Working alongside Anton Vanko, Howard Stark began to develop the first Arc Reactor and eventually created an industrial sized Arc Reactor that powered the Stark Industries Headquarters in the 1960’s. While this Arc Reactor provided clean energy, it was inefficient and incredibly expensive to run. Howard Stark had developed a theoretically element that would effectively and efficiently power the Arc Reactor but he unable to synthesize the element due to the constraints of the technology of his time. He would leave a blueprint for his son, Tony Stark, and with that blueprint, Tony managed to create the new element needed to power his mini Arc Reactor without poisoning him and allowed him to complete a new Arc Reactor that powered Stark Tower with 100% clean energy.
Palladium Mini-Arc Reactor I – Iron Man – Tony Stark was critically wounded and kidnapped in an ambush by the Ten Rings terrorist organization. In order to save his life Ho Yinsen put an electromagnet in Stark’s chest to keep the shrapnel from reaching Stark’s heart and killing him. Raza, the leader of the Ten Rings, demands that Tony build him a Jericho missile. Instead, Tony and Yinsen secretly design and build the first miniature Arc Reactor to power the electromagnet in his chest, followed by the first Iron Man armor. the Palladium Mini-Arc Reactor I powered the small engine that ran the internal systems of the MARK I and provided limited flight capabilities to the suit. Upon returning to the States, Tony developed the Palladium Mini-Arc Reactor II and once installed tells Pepper to “destroy it…incinerate it”. Pepper does not destroy it, instead presenting the Reactor in a case to Tony as proof that he has a heart.
The Palladium Mini-Arc Reactor I was not built for sustained flight or combat as the flight from Stark’s mansion to Stark Industries drained over 80% of the Reactors power and the subsequent fight with Obadiah Stane in the Iron Monger suit drained the remaining power from the Arc Reactor.
Palladium Mini-Arc Reactor II – Iron Man – Upon return from his kidnapping, Tony put his considerable resources into creating a second, more advanced mini-Arc Reactor that was exponentially stronger than its predecessor. With a stronger mini-Arc Reactor that would allow for sustained flight, Tony began development and construction of the MARK II and on completion, immediately took the armor on its initial flight. Tony followed his success with the MARK II with the creation of MARK III armor, which he eventually flew to Gulmira, where he liberated the town from the Ten Rings and destroyed the Stark Industries’ weapons in the organization’s possession. The Palladium Mini-Arc Reactor II was then stolen by Obadiah Stane to power his Iron Monger armor. Tony managed to retrieve the retired Palladium Mini-Arc Reactor I and with it managed to defeat Stane in the Iron Monger armor.
Palladium Mini-Arc Reactor III – Iron Man 2 – presumably built immediately after the Duel of Los Angeles, as the Palladium Mini Arc Reactor II was destroyed during the Duel and Tony needed a new power source for both his electromagnet and suits. Obadiah Stane’s theft of the Palladium Mini Arc Reactor II led Tony to build independent mini-Arc Reactors to power the MARK II, restored MARK III and presumably the MARK IV, although the timeline on when Tony stopped using the mini-Arc Reactor in his chest is murky. The MARK V was powered by the mini-Arc Reactor in Tony’s chest, dramatically increasing the effects and spread of Tony’s Palladium poisoning.
Vanko’s Mini-Arc Reactor I – Iron Man 2 – presumably powered by Palladium like Tony’s original Arc Reactor, Ivan Vanko fashioned his mini-Arc Reactor from blueprints his father had in his possession from the time the elder Vanko spent designing the original Arc Reactor with Howard Stark. Driven by the desire to tarnish Tony and Stark Industries legacy, Vanko uses his mini-Arc Reactor to power to whip-like energy weapons and attacks Tony leading to the Duel of Monaco. Utilizing the portable MARK V, Tony manages to defeat Vanko in the Whiplash I armor and Vanko is taken into custody.
Vanko’s Mini-Arc Reactor I powered the Whiplash MARK I armor.
New Element Mini-Arc Reactor I – Iron Man 2 – after being alerted to Tony Stark’s imminent death due to Palladium poisoning from his mini-Arc Reactors, Nick Fury supplies Tony with a blueprint from his father, Howard Stark. Tony uses these blueprints to synthesize a new element to power his mini-Arc Reactor that cured him of his Palladium poisoning. This new element made this new mini-Arc Reactor exponentially stronger than it’s predecessor and did not poison him like the previous Palladium Mini-Arc Reactors. To capitalize on this new power source, Tony designed the MARK VI which saw major advancements to the suit’s speed and weapons systems due to the increased power of the new mini-Arc Reactor. This mini-Arc Reactor went on to power the MARK VII, one of the most advanced and well equipped suits Tony built.
Vanko Mini-Arc Reactor II – Iron Man 2 – after freeing him from captivity, Justin Hammer allows Ivan Vanko access to his resources in a hope that Vanko will produce Iron Man suits for him. Vanko instead builds Hammer a set of drones and builds himself a stronger mini-Arc Reactor and the Whiplash MARK II armor. Vanko coordinates an attack on Tony Stark and the Stark Expo with the Hammer Drones and then Vanko attacks Tony and James Rhodes, in the War Machine armor, himself. A fight ensues with Stark and Rhodes eventually coming out as the victors, killing Vanko and destroying his second mini-Arc Reactor.
Vanko’s Mini-Arc Reactor II powered the Whiplash MARK II armor.
New Element Arc Reactor – Marvel’s Avengers – in-between the events of Iron Man 2 and Avengers, Tony began construction on Stark Tower and a new Arc Reactor to power it. Once Stark Tower was complete, Tony powered the newly, redesigned Arc Reactor with the new element he discovered in Iron Man 2. With this new element, the new Arc Reactor would have been able to keep Stark Tower running for over a year with clean energy. Instead, Loki uses the energy from the new Arc Reactor and the Tesseract to open the wormhole above New York that allows for the Chitauri invasion and resulting Battle of New York.
New Element Mini-Arc Reactor II – Iron Man 3 – with the exception of the Nano-Arc Reactor, the New Element Mini-Arc Reactor II is the strongest mini-Arc Reactor and appears to be the pinnacle of the mini-Arc Reactor technology. Designed to power the many different functions of the Iron Legion, the New Element Mini-Arc Reactor II is the strongest and most efficient mini-Arc Reactor Tony built. Every suit in the Iron Legion and all of the succeeding main suits possess their own independent mini-Arc Reactor.
The New Element Mini-Arc Reactor II powers the Iron Legion, MARK 42, MARK 43, MARK 44, MARK 45, MARK 46, MARK 47 and MARK 49.
New Element Nano-Arc Reactor I – Avengers: Infinity War – This new “nano”-Arc Reactor is the most to date advanced to date. It is a detachable Arc Reactor filled with nanoparticles and the armor can be deployed in an instant with Tony’s thoughts. The MARK L is made up of billions of nanoparticles but the suit is still the most durable, flexible and powerful armor to date.
The New Element Nano-Arc Reactor powers the MARK L.