A lot of these answers are only partially correct and some have incorrect information in them. I'll try to clarify.

It's important to understand that chord quality and construction is independent of scales. Yes, both are defined by intervals, but their construction is mutually exclusive.

A scale is a sequence of intervals. In western music, there are Major scales and three types of Minor scales. Each type has a unique sequence of intervals that define it (as many of the posts here discuss). A scale can become a Key when the root note is assigned. For example, the Major scale becomes the key of "C Major" when you define "C" as the tonic of it. But all of this is irrelevant to chord construction.

Chords are also constructed of sets of intervals. Chords are simply 3 or more intervals intended to be played in unison (or rapid sequence as in strumming a guitar). A Major chord is defined as the Unison, a Major 3rd, and the Perfect 5th (technically a Major 3rd above the first Major 3rd). Technically, these are not intervals of a scale, though a lot of people think of them that way. They are simply the number of semi-tones (or half-steps, if you like) between the notes.  

Triads are very specific types of chords using exactly the Unison, a Major or Minor 3rd above it, and a Major or Minor 3rd above that (which ends up being the Prefect 5th when using Major 3rds). A Major chord is a type of Triad, but a Seventh chord is not (because it has 4 intervals).  Some chords have upwards of 7 or more intervals.

Finally, it doesn't matter which scale you are using, the chord constitution will always be the same. When playing a C Major chord on a piano, you will *always* play the same 3 physical keys (the C key, E key, and G key) regardless of which scale / Key you are playing in. The *only* thing that would change based on the key (i.e. scale) would be the note names of those 3 keys, but the physical pitches will always be the same.

If you are looking for which intervals chords are constructed from, this page lists a couple of dozen chord types and their intervals:
https://www.internetchorddatabase.com/Reference.aspx