Li ne scias, ĉu riveli la negativon aŭ ne.

Ĉu introduces an indirect yes/no question. In this sentence, Li ne scias, ĉu ... aŭ ne means He doesn't know whether ... or not.

A native English speaker often thinks of if, but in Esperanto:

• ĉu = whether / if in a question sense
• se = if in a conditional sense

So:

• Li ne scias, ĉu riveli la negativon aŭ ne. = He doesn't know whether to reveal the negative or not.
• Se li rivelos la negativon, ... = If he reveals the negative, ...

Using se here would normally be considered wrong in careful Esperanto.

Because Esperanto can use a question word + infinitive construction, much like English:

• kion fari = what to do
• kien iri = where to go
• ĉu resti aŭ foriri = whether to stay or leave

So ĉu riveli la negativon aŭ ne means whether to reveal the negative or not.

The subject of riveli is understood from context. Here, it is most naturally the same person as li.

A fuller version could be something like:

• Li ne scias, ĉu li rivelu la negativon aŭ ne.

That version is more explicit, but the infinitive version is natural and concise.

The -n marks the direct object.

Here, la negativon is the thing being revealed, so it is the object of riveli:

• riveli ion = to reveal something
• riveli la negativon = to reveal the negative

Even though riveli is an infinitive, it still takes its own object in the normal way.

Ĉu already shows that there is uncertainty, but aŭ ne makes the alternative explicit: or not.

So:

• Li ne scias, ĉu riveli la negativon. = He doesn't know whether to reveal the negative.
• Li ne scias, ĉu riveli la negativon aŭ ne. = He doesn't know whether to reveal the negative or not.

Both are possible. The version with aŭ ne sounds a little more complete or emphatic.

In Esperanto, ne normally goes directly before the word or part of the sentence it negates.

So:

• Li ne scias = He does not know

Here, ne negates the verb scias.

If you moved ne elsewhere, the meaning would change or the sentence would become unnatural.

Not exactly in function, although it is the same word.

• The first ne directly negates the main verb: He does not know
• The final ne is part of the expression aŭ ne = or not

So the first one is the main sentence negation, while the second one completes the choice inside the indirect question.

Because ĉu riveli la negativon aŭ ne is a subordinate clause, and Esperanto commonly separates such clauses with a comma.

So the structure is:

• Li ne scias = main clause
• ĉu riveli la negativon aŭ ne = subordinate clause

Comma use in Esperanto is fairly regular before subordinate clauses introduced by words like ĉu, ke, kiam, ĉar, and so on.

La is the definite article, meaning the.

So la negativon refers to a specific negative, not just any negative in general.

Compare:

• riveli negativon = reveal a negative / some negative
• riveli la negativon = reveal the negative / that specific negative

So the sentence is talking about a particular thing already known in the context.

Yes. A more explicit version could be:

• Li ne scias, ĉu li rivelu la negativon aŭ ne.

Here rivelu is in the volitive form, which can be used in subordinate clauses to express what someone should do, is to do, or might choose to do.

The difference is roughly:

• ĉu riveli ... = whether to reveal ...
• ĉu li rivelu ... = whether he should reveal / whether he is to reveal ...

The infinitive version is shorter and very common when the subject is understood.

Yes, negativa is the adjective negative, but Esperanto can easily turn many roots into nouns with -o.

So negativo is a noun meaning a negative. Depending on context, it could mean different things, such as:

• a photographic negative
• a negative answer or result
• something negative in a more abstract sense

Since you already have the meaning from context, the important grammar point is that negativo is simply the noun form, and negativon is that noun in the accusative.