why are there people who say that she needs cdr when in the first 2 main items u have %40

Also Badass of lol stop up voting bad builds begging for rep and upvotes get them through actually being good at the game and being nice on the forums you'll get rep when you deserve it.

Really not good I'm not downvoting just to make other builds look good this is just bad. Heal is pretty bad alone and especially when you don't have an escape other than Celerity. You put 8 into offense not even getting the best part (Archaic Knowledge) and instead you spec into the horrible Heal. Rabadons is good but 3 is stupid their Unique Passive doesn't stack. Sure it will give the most AP but it would be better to go with something with 50-80 less AP and another good Passive / stat, also Rabadons is SUPER expensive. All in All bad build

lol?

there's something important that you missed within this guide. It's great that your stacking AP and its great that you can do damage but that's not sona's role.
it is percisely because of guides like this (not saying it is your fault) that people guild Sona as some sort of nuke. Sona is purely a support gifted with a pretty devastating poke when necessary.
I do agree with stacking AP as sonaMs skills scale very ****pily off her AP and the main key to survivability to her is positioning. Never be at the front line or mid lines of the battle, stay far enough to run, yet close enough to heal and stun
mana regen runes will not keep up with sona if you spam heals and poke left and right like i do. of course you prioritize healing your party over poking, but ive realized sona is a terrific early game harasser with the passive off of hymn of valor and power chord.
the best guide that i've seen had the core build for her as; Tear of Godess, mejai soulstealer, (boots of swiftness/sorcerer/mercury), lich bane. later in the game turn the ToG into AA staff. i prefer boots of swiftness because then im able to catch up to my team faster and run away faster.
after that is really up to the situation, if your team is doing great, no one can get through your team to you, get a rabadon. if you feel too squishy get a banshee's veil or force of nature. they key to sona's survivability is positioning and cooperation with your teamates. i always get saved by my teamates because they love my heal and stun.
i go with CD reduction runes and some mana regen and magic pen runes. this allows my ulti to reach about 90 sec CD and 60 sec with full mejai and blue buff, its terrific!
Sona is a support as her base line. dont get me wrong she can hit hard, but she's built as a support to aid her team. I work extremely well with nearly every champion as sona due to the very low CD heals which heal a decent amount, occasional hurtful poke, and the devastating stun. song of celerity i find using to chase, run, catch up mostly

Stacking Rabadon's is wasteful, the mana regen is unnecessary for the total mana included in your build, unless you're literally spamming the entire time. Perhaps replace one of the Rabadon's with an AAS? Also, as you stated, Sona is squishy, especially if you build her like this. A good build should emphasize the strengths of champions and also compensate for weaknesses.

Awful. Too much AP you can't do anything with because you're gonna be dead before you can cast a spell. The second Rabadon's, and even suggesting getting a third is ridiculous with a SUPPORT champion.

Sona needs cooldown reduction, mana regen, and some survivability. Just a little AP will do for heals.

Rep me if you think that Badass Prince Of LOL is annoying judge

Too much Mana, Sona needs cool down and Ap, Cool down fast enough to heal your team mates, mana regen seals for mana regen simple, for Quaints for Health survival, and Items I'd get just Ap for healing team mates. Really even though you have enough mana for you skills you just don't heal enough from a person getting ignited or do enough damage with your ult, get some escape build and try harder next time before posting this.

+Rep me

If you thumbs up my build too it will be great ^^ im good with you,can you be good with me too?be kind?thumbs up my build?o_O?PLS?

Lol the downvoting, tbh I don't find the build bad at all, sona has very very very high range so she can heal and deal damage far of the enemy's carry.

I think you need magic pen marks and clairvoyance, but the rest of the build is good