i ve got some question regarding naming the scale's chords
for example we have c major scale which the notes are c d e f g a b and the degrees are I II III IV V VI VII
according to chord construction theory i can take first , third , and fifth degrees
which if i start from c will be c e g i read that this chord name is c major
and if i start from second degrees of scale then it will be d f a and here is my problem
why those it become d minor?? how is the naming rule ?
and another question about chord progression what is the rule for chord progression? and how to use scales and their relative chords for soloing according to chord progression?
thanks very very much in advance
Harmonised major scale- M m m M M m o M

Relative minor is the six so C's is Am. Use A natural minor - its the same as C major AKA Aeolian mode. If I understood your question (I don't think I did) then here are your answers.
The major scale degrees are I ii iii IV V vi vii
The upper and lower case represent major/minor.

You need to take a cloer look at the intervals between the notes of the chords that are created, this will tell you if they are major or minor.

The first chord is made from C E G.
C to E is a major 3rd - This makes the chord Major.

For the 2nd chord - D F A, you will notice that the 3rd - F - is one half step closer to the root and one half step further away from the 5th.

The interval from D to F is a minor 3rd - therefore the chord is minor.

The reason the pattern of Major Minor Minor Major Major Minor Diminished is created is because of the distances between the scale degreed - WWHWWWH.

now, ask more
fast answer and thanks so much
shed some light on it
about the pasttern you said (Major Minor Minor Major Major Minor Diminished ) is it just for c major scale? or all the major scale?
and about my second question how to know which chord should come after each other in chord progression ? and how use scales and chord progression for soloing?

thanks alot
all major scales are the same, the same patterns can be moved anywhere on the fretboard.

the chords created are-
Major7 r 3 5 7
Minor7 r b3 5 b7
Minor7 r b3 5 b7
Major7 r 3 5 7
7 r 3 5 b7
Minor7 r b3 5 b7
Min7b5 r b3 b5 b7

play these chord progressions-
I - IV - V (C F G)
I - vi - V (C Am G)
I - V - IV (C G F)

you can pick up on some of the strong movements.
The strongest movements are 4ths and 5ths, you will notice C F G and back to C is very strong, this is root, 4th, 5th, root.

Going from the 5th to the root is the most common ending to a song, it is known as a full cadence, go to wikipedia and read up on cadences, or read a lesson on this site.

once you are happy with the chords created, learning different cadences will give you some really fun chord combos to play.

scales for soloing over progressions? i personally advise to start by using the major scale that created the chords in the first place, or the corresponding pentatonic.