To the best of my knowledge copyright applies only to lyrics and to melody. Individual words cannot be copyrighted but phrases could be on shakey ground if they are not common phrases and used in a similar way involving a hook.
Chords are fine, there is no copyright applied to chord sequences and in fact, it is a common way to shadow write. Take the chords from a song and apply new melody, lyrics, timeing of chord changes and voila, you have a new song.