O relógio está pendurado na parede.

In European Portuguese, we almost always place a definite article before concrete, countable nouns when they are specific.

• O relógio translates literally as “the clock.”
• In English you might drop “the” (“Clock is hanging…”), but in Portuguese that sounds odd.
• You’d do the same with a cadeira, o livro, etc.

Portuguese distinguishes between ser (essential/permanent traits) and estar (states, conditions, locations).

• Está marks a temporary state or location: O relógio está na parede (“The clock is on the wall”).
• Ser would sound unnatural here; you’d only use é for identity or inherent characteristics (e.g. O relógio é de madeira).

Pendurado is the past participle of pendurar (“to hang”), used adjectivally.

• estar + past participle indicates a resulting state: something has been hung and remains so.
• It functions like “hung” in English: The clock is hung on the wall.
• To describe the action of hanging, you’d say está a ser pendurado or use an active form.

Na is a contraction of em + a:

• em a parede → na parede
• Similarly, no = em o, nos = em + os, nas = em + as.

Generally no. In Portuguese:

• sobre implies “over” or “above” in a more abstract/poetic sense, not attachment.
• na parede is the natural way to say “on the wall” when something is fixed or hanging.
• If you want “on top of” a horizontal surface you use sobre (e.g. sobre a mesa).

Yes. As an adjective (past participle used adjectivally), it agrees with the noun:

• Feminine singular: pendurada (e.g. A lâmpada está pendurada)
• Masculine plural: pendurados
• Feminine plural: penduradas

In a normal sentence, no. Omitting the article sounds ungrammatical:

• You could see that in headlines or labels (e.g. signage), but not in regular speech or writing.
• The rule is to include the definite article with specific, countable nouns.

Yes, depending on nuance:

• O relógio fica pendurado na parede also works; ficar can express location or resulting position.
• More formal: O relógio encontra-se pendurado na parede.
• You could also say O relógio está preso na parede (implying it’s screwed or nailed).