وَإِذَا ٱلْجَحِيمُ سُعِّرَتْ
Sentence structure
Hellfire is nominative in the coordinated condition, and سُعِّرَتْ is a Form II passive perfect explaining its kindling.
Ayah summary
Hell will be kindled with full intensity.
وَإِذَا — And when
Grammar: وَ coordinates the whole conditional construction with the preceding one. إِذَا is a future non-jussive temporal adverb containing conditional meaning.
ٱلْجَحِيمُ — the Hellfire
Grammar: The noun is nominative; here it is the deputy subject of an omitted passive verb explained by سُعِّرَتْ.
سُعِّرَتْ — is set ablaze
Grammar: A Form II feminine singular perfect passive verb. The written verbal clause is explanatory and has no syntactic position.