Hi! Neat deck(I love Izzet), I have some ideas that might make it better.
Shock is pretty inefficient for the slot and cost, and
lightning bolt is legal in modern. If you're worried about cost then don't, every player whoever plans on making a red deck ever should buy 4x bolts because of how useful and cheap they are now.
Mizzium mortars is amazing removal and running 2 is great in a control deck. With all the colorless mana spells you have I would recommend running 2x
Goblin Electromancer because it makes the deck run smoother and makes X spells not so inefficient. If you like the X spell then I would switch the Volcanic Geysers to
Banefire(Can't be countered),
Devil's Play(Flashback), or
Heat Ray(Instant.) Also running 2x
Isochron Scepter is amazing(like one of the best cards in the deck) in a control deck because it allows you to imprint a
Lightning Bolt or
Counterspell into in and use it every turn for 2 mana which can completely shut down decks and let you win the game from this card alone. A slight upgrade would be to switch the Izzet guildgates to
swiftwater cliffs, then plan to get
sulfur falls,
steam vents, and/or shivan reefs for this one and future red/blue decks. It would also be good to at least sideboard
counterflux for when your opponent runs counters.
Young Pyromancer is nice for developing a board.
Quicksilver dagger is nice to throw on a
guttersnipe or electromancer because you often don't want to attack with them because they'll die to your opponent's board, but this will let you tap them for 1 face damage and more importantly card draw. A couple more cards to consider are:
Galvanoth,
Djinn Illuminatus,
Hypersonic Dragon,
Snapcaster Mage,
Teleportal, and both copies of Niv-Mizzet(
Niv-Mizzet, the Firemind/
Niv-Mizzet, Dracogenius.)
Anyway nice deck, hopefully I was of some help to you.