The Arc Reactor was a power core made out of paladium, and was the initial source of the first Iron Man Mark suits, and was later modified to an advanced level by Tony to power his suits, as it kept on improving. The second arc reactor is made of a element that Tony Stark created in the second movie.
Original Arc ReactorEdit
Created by Howard Stark, the Large Arc Reactor powered Stark Industries for years before Tony created his mini versions, though it was never replicated. Unable to defeat Iron Monger, Tony lures him to the roof of Stark Industries and has Pepper Potts overload the reactor, sending up an energy surge that disables the suit and knocks out Obadiah Stane. Stane and his suit then fall into the reactor, which explodes, killing and incinerating Stane and his suit. Tony later uses a Vibranium version to power Stark Tower and it is used by Loki to power the Tesseract to create a wormhole to bring a Chitauri invasion force to Earth.
Palladium Mini-Arc Reactor Mark IEdit
Tony creates the Palladium Mini-Arc Reactor Mark I to power the electromagnet keeping shrapnel from reaching his heart in lieu of a car battery. He later uses it to power his Mark I suit, but upgrades to his Mark II reactor and abandons this one. Rather than throw it out, Pepper Potts frames it with the note "Proof Tony Stark Has A Heart." After his Mark II reactor is stolen by Obadiah Stane, Tony, with the help of his robot Dummy, plugs back in this reactor and uses it to power the Mark III suit in battle against Iron Monger, but it is not designed to work with that suit and quickly runs out of power. However, with Pepper's help, Tony defeats Iron Monger and kills Stane. He replaces this reactor with the Mark III later.
Palladium Mini-Arc Reactor Mark IIEdit
Created by Tony Stark after returning home, the Palladium Mini-Arc Reactor Mark II is used to power his electromagnet and his Mark II and Mark III suits. After finding the Mark I suit and rebuilding it into the Iron Monger, Obadiah Stane steals this reactor to power it as he is unable to replicate the technology. Tony faces him using the Mark I, but is inadequate to power his suit properly. Finally, Tony has Pepper Potts overload the Large Arc Reactor powering Stark Industries and Stane, his suit and this reactor are incinerated in the explosion.
Palladium Arc Reactor Mark IIIEdit
The Palladium Arc Reactor Mark III was the reactor used by Tony to power his armors and electromagnet in the movie, Iron Man 2. Presumably created to replace the one stolen from him by Stane and eventually replaced by an improved reactor as the palladium was slowly poisoning Tony to death. Each of his armors had one of these powering it rather than relying on the one powering his electromagnet to do both, allowing James Rhodes to steal the Mark II suit.
New Element Arc Reactor Mark IEdit
The new element Arc Reactor Mark I was the Arc Reactor created by Tony after he re-discovered an element, and tried to synthesize it, resulting to the new and more powerful clean energy.
New Element Arc Reactor Mark IIEdit
Tony eventually replaced the Mark I reactor with the Mark II to power his Iron Legion and electromagnet. The ones powering the Iron Legion were destroyed when Tony had J.A.R.V.I.S. self-destruct the suits and after having the shrapnel removed from his chest, Tony pitches the one powering the electromagnet into the sea.
Needing something better to power the electromagnet keeping the shrapnel in his chest from reaching his heart and his planned Mark I suit, Tony builds his first Mini-Arc Reactor based off the large one powering Stark Industries. Using it, he succeeds in escaping and later upgrades to the Mark II version while the Mark I is framed by Pepper Potts as proof that Tony does have a heart.
Tony uses the new arc reactor to power his Mark II and Mark III suits, but has it stolen by Obadiah Stane to power his own Iron Monger suit. Tony reclaims his Mark I reactor and uses it to power the Mark III in battle against Iron Monger.
The reactor isn't powerful enough to power the suit for long so Tony has Pepper overload the Large Arc Reactor, creating an energy surge and explosion that kills Stane and destroys the Mark II reactor while the Mark I runs out of power. Tony later creates the Mark III reactor to replace his destroyed Mark II.
The palladium in the reactor is slowly poisoning Tony to death. He has created arc reactors to power all of his suits, allowing James Rhodes to steal the Mark II suit and turn it into War Machine. He later creates a new reactor made of a new element that no longer poisons him and greatly increases the power he has access to. To match this, he creates the Mark VI suit which takes advantage of the greater power for increased capability. Ivan Vanko also creates his own arc reactors to power his whips and armor which he knows how to do as his father was Howard Stark's partner in creating the first arc reactor.
During the final battle, Pepper takes down the Mark IX suit by punching through its arc reactor. The arc reactors powering the Iron Legion are destroyed when J.A.R.V.I.S. self-destructs the suits. Tony later has surgery to have the shrapnel removed from his chest with an arc reactor powered electromagnet catching the pieces once they are removed. Afterwards, as the arc reactor is no longer needed to power the electromagnet, Tony pitches it into the sea.
- The Arc Reactor is based on the reactor of the same name in the comics, both having almost the same appearance and functionality.
- In the Iron Man 2 novelization, the element created for the new arc reactor is referred to as vibranium. However, in the movie continuity, vibranium is a metal compound from the region of Wakanda that was used to create Captain America's shield; it was not an element created by Howard Stark and used in the arc reactor. Therefore, the element in the new arc reactor has yet to be named.
- The physical reaction experienced by Tony when he inserts the New Element Arc Reactor into his body does not correspond to how normal heavy metal poisoning works. While he would not have continued to become sicker once the palladium reactor was removed, a multi-month course of treatment should have been needed to remove the material already in his body.
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