وَإِذَا ٱلْقُبُورُ بُعْثِرَتْ
Sentence structure
In this coordinated condition, ٱلْقُبُورُ is the deputy subject of an omitted passive verb, while بُعْثِرَتْ is the explanatory written clause.
Ayah summary
The graves will be overturned and the dead will be brought out.
وَإِذَا — And when
Grammar: وَ coordinates the clause; إِذَا is a future non-jussive temporal adverb.
ٱلْقُبُورُ — the graves
Grammar: A nominative definite plural noun; here it is the deputy subject of an omitted passive verb.
بُعْثِرَتْ — are overturned
Grammar: A quadriliteral feminine singular perfect passive verb; the written clause is explanatory here.