O placar mostra um empate.

Placar usually means scoreboard or score in a sports context.

In this sentence, it most naturally refers to the scoreboard/display that shows the current result. But in Brazilian Portuguese, placar can also mean the score itself.

Examples:

• O placar está 2 a 1. = The score is 2–1.
• Olha o placar! = Look at the scoreboard / Look at the score!

So placar can refer either to the board/screen or to the numbers shown on it.

Portuguese uses articles much more often than English does.

So where English might say Scoreboard shows a tie in a headline-like style, normal Portuguese usually prefers O placar mostra um empate.

Here:

• o = the
• placar = scoreboard / score

Also, nouns in Portuguese are usually learned together with their article:

• o placar
• not just placar

That helps you remember both the meaning and the grammatical gender.

Because placar is a masculine noun in Portuguese, so it takes o in the singular:

• o placar
• um placar

There is not always a logical reason for a noun’s gender, and placar is one you mostly just memorize. A good habit is to learn nouns with their article:

• o placar
• o empate
• a partida
• a tela

Mostra is the third-person singular present tense of mostrar.

Conjugation:

• eu mostro
• você/ele/ela mostra
• nós mostramos
• eles/elas mostram

In this sentence, the subject is o placar, which is singular, so the verb is also singular:

• O placar mostra...

So the structure is:

• subject: o placar
• verb: mostra
• object: um empate

Because the subject is singular.

The subject is o placar = the scoreboard / the score, which is one thing, so Portuguese uses the singular verb:

• O placar mostra... = singular
• Os placares mostram... = plural

Compare:

• O placar mostra um empate.
• Os placares mostram resultados diferentes.

Empate is a noun meaning tie or draw.

It is masculine:

• o empate
• um empate

Here, um empate means a tie. Portuguese often uses the indefinite article the same way English does with countable nouns.

So:

• mostra um empate = shows a tie

You will also see empate in sports phrases like:

• O jogo terminou em empate. = The game ended in a draw.
• Foi um empate sem gols. = It was a scoreless draw.

Usually, O placar mostra um empate is the more complete and standard version.

Leaving out um can happen in very compressed styles such as:

• headlines
• sports captions
• fast commentary

But for a learner, um empate is the safest and most natural choice in a full sentence.

So:

• O placar mostra um empate. = normal full sentence
• O placar mostra empate. = possible in some contexts, but less standard in everyday neutral speech

Because empate and empatado are different kinds of words.

• empate = a noun = a tie / draw
• empatado = an adjective or past participle = tied

This sentence uses the noun:

• O placar mostra um empate.

If you want to describe the state of the game, you often use empatado:

• O jogo está empatado. = The game is tied.
• Os times estão empatados. = The teams are tied.

So Portuguese has two common ways to express this idea:

• There is a tie → há um empate / o placar mostra um empate
• The game is tied → o jogo está empatado

Yes, it is natural and understandable.

It sounds especially appropriate in contexts like:

• sports commentary
• apps or websites showing scores
• describing what appears on a screen

Some other natural alternatives are:

• O placar indica empate. = The scoreboard indicates a tie.
• O jogo está empatado. = The game is tied.
• O placar está empatado. = The score is tied.

The exact choice depends on what you want to emphasize:

• mostra focuses on what the scoreboard displays
• indica sounds a bit more formal
• está empatado focuses on the game’s current state

A rough pronunciation guide is:

o pla-KAR MOS-tra um em-PA-ti

A few useful notes:

• placar has stress on the last syllable: pla-KAR
• mostra has stress on MOS
• empate has stress on PA

In many Brazilian accents:

• the r at the end of placar sounds softer, often somewhat like an English h
• te at the end of empate often sounds like chi to English ears, especially in much of Brazil

So you may hear something closer to:

• u pla-KAH MOS-tra um em-PA-chi

Also, the article o often sounds more like u in normal speech.

They are related, but not exactly the same.

• placar = the score / scoreboard, especially the numerical result during or after a game
• resultado = result, a broader word

Examples:

• O placar está 1 a 1. = The score is 1–1.
• O resultado foi surpreendente. = The result was surprising.

So in a sports sentence about what the board displays, placar is the better word.
If you are talking more generally about the outcome, resultado may fit better.