well, seems pretty right, but in the case of the B note, you have to remember that F, in relation to B, is the flattened (diminshed) 5th. so it wouldn't be a minor triad, it'd be a *diminished* triad, which is essentially a minor triad with a flattened (diminished) 5th, hence the name.
if you played C major over a straight 1-3-5 B minor chord (B-D-F#), there would be a strange tension between the F you're playing and the F# in the accompaniment.
but other than that, i can't see anything else wrong, good job. now harmonize every other major scale in all 12 keys! NOW! LOL
a good practice to apply these is to learn em on piano. if you take the same 1-3-5 triad shape and played it over all the white keys, you'd get those 7 chords you played. then try a key close to C major (F major, one flat in the key signature only, or G major, only one sharp in the key signature) and harmonize those in root position triads (1-3-5). keep doing it in all keys till you get to a key like C# major where its pretty much all black notes.
now if you are hopeless at piano (which i sorta am LOL), you could just play these triads in every key on the neck, but say the names of each note you're playing, and the degree of the scale its in. like you hit a D minor triad in the key of C major, you say "D, F, A: D minor, 2nd degree of the C major scale" and so on.
this is just one silly exercise i just came up with now, but if you want to try other things, perfect. learning another instrument like piano helped me alot, because it made the guitar make more sense, but if you don't, that's fine as well.
steve vai said he was always hopeless at keyboard playing too... but i guess that was more incentive for him to become a freak on guitar :biggrin:
either way, good luck, and don't forget to ask questions, because this stuff might seem easy, but it takes a little while to internalize and become instantly accessible.
-Pryde