O ás do naipe ficou no monte.

Ás means ace in card games.

The accent matters because it distinguishes this word from other very common forms:

• as = the for feminine plural nouns
• às = contraction of a + as, often meaning to the / at the

In ás, the acute accent marks the stressed vowel and helps show that this is a different word. So o ás is the ace, not anything related to as or às.

Portuguese often uses the definite article where English might leave it out.

So o ás is the normal way to say the ace. In a specific context, especially when talking about a particular card, the article sounds natural.

Also, ás is a masculine noun, so it takes o:

• o ás
• not a ás

Naipe means suit in a pack of cards, such as:

• copas = hearts
• espadas = spades
• ouros = diamonds
• paus = clubs

So do naipe means of the suit. In context, it refers to the suit being talked about.

Because Portuguese normally contracts de + o into do.

So:

• de + o = do
• de + a = da
• de + os = dos
• de + as = das

That is why you get o ás do naipe instead of o ás de o naipe.

Ficou is the pretérito perfeito of ficar.

For ficar:

• eu fiquei
• tu ficaste
• ele/ela/você ficou
• nós ficámos
• vós ficastes
• eles/elas/vocês ficaram

Here, ficou shows a completed event in the past: the ace ended up, remained, or was left in the pile.

In this sentence, ficou can be understood as something like:

• stayed
• remained
• was left
• ended up

The best choice depends on the context of the game.

That is very common with ficar in Portuguese: it often expresses the idea of a resulting position or state. So the card came to be in that place and remained there.

In card-game language, monte usually means a pile or stack of cards.

Depending on the game, it could be:

• the main pile
• the stock pile
• a heap of cards on the table

It is not exactly the same as baralho, which usually means the deck/pack of cards as a whole.

Because no is the contraction of em + o:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

So no monte literally comes from em o monte.

Portuguese often uses em where English might say in, on, or sometimes at. With card piles, no monte is the natural expression.

Sometimes, but the meaning shifts a little.

• no monte suggests the card is in the pile / as part of the pile
• sobre o monte suggests it is on top of the pile

So if the idea is simply that the ace remained in that pile, no monte is the better choice. If you specifically mean physically on top, sobre o monte could work.

Yes. The neutral order is:

• O ás do naipe ficou no monte.

But Portuguese can move parts of the sentence for emphasis, for example:

• No monte ficou o ás do naipe.

That sounds more marked and may emphasize where the ace ended up. The original version is the most straightforward and neutral.