Voy a atar los globos a la silla.

Because Spanish often drops subject pronouns when the verb already shows who the subject is.

• voy = I go / I’m going
• So Voy a atar... already tells you the subject is I

You could say Yo voy a atar los globos a la silla, but yo is usually unnecessary unless you want emphasis or contrast.

It is the ir a + infinitive structure, which is a very common way to talk about the near future or an intended action.

• voy = I go
• a = part of the future structure here
• atar = to tie

So voy a atar means I’m going to tie.

This is extremely common in everyday Spanish, often more common in speech than the simple future.

Because after ir when you use this future construction, Spanish requires a:

• voy a comer
• vamos a salir
• va a llover

So voy a atar is correct, but voy atar is not.

They do two different jobs:

• The first a is part of voy a atar, the future construction: I’m going to tie
• The second a links the thing being tied to where it is being tied: to the chair

So:

• Voy a atar = I’m going to tie
• los globos a la silla = the balloons to the chair

It may look repetitive to an English speaker, but it is completely normal in Spanish.

Spanish uses articles much more often than English.

Here:

• los globos = the balloons
• la silla = the chair

Even when English might sometimes sound natural without an article in a broader context, Spanish often still uses one. In this sentence, the articles sound completely normal and expected.

Atar means to tie, to fasten, or to bind.

In this sentence, it means physically fastening the balloons so they stay attached to the chair.

Some related verbs are:

• atar = the most general everyday verb for tie
• amarrar = also to tie / fasten, but can sound a bit more like secure firmly, and usage varies by region
• anudar = to knot, more specifically about making a knot

For this sentence, atar is a very natural choice in Spain.

Here it means to the chair in the sense of attached to the chair.

It does not mean on the chair. If you wanted on the chair, you would usually say:

• en la silla = on the chair / in the chair depending on context

So:

• atar los globos a la silla = tie the balloons to the chair
• poner los globos en la silla = put the balloons on the chair

Because of how the sentence is structured:

• atar takes a direct object: the thing you tie
• Here, that direct object is los globos
• a la silla tells you what they are being tied to

So the pattern is:

• atar + thing + a + place/object

Examples:

• Ató el perro al árbol = He tied the dog to the tree
• Ató la cuerda a la puerta = She tied the rope to the door

In your sentence, the balloons are the thing being tied, and the chair is what they are attached to.

Yes. Ataré los globos a la silla is grammatically correct and means I will tie the balloons to the chair.

The difference is mainly one of style and feel:

• Voy a atar... = very common in conversation; often feels more immediate or planned
• Ataré... = simple future; can sound a bit more formal, more definite, or sometimes more like I will

In everyday spoken Spanish, especially in casual contexts, voy a atar is often the more natural choice.

Yes, but the original order is the most straightforward and natural:

• Voy a atar los globos a la silla

You may also hear variations like:

• Voy a atar a la silla los globos

That is possible, but it is less neutral and may sound more marked or stylistically different. For a learner, the original order is the safest one to use.

A simple guide is:

• Voy ≈ boy
• a = short ah
• atar = ah-TAR
• los = lohs
• globos = GLO-bohs
• a = ah
• la = lah
• silla = usually SEE-ya in most of Spain

A few useful notes:

• v in voy is pronounced more like a soft Spanish b, not a strong English v
• ll in silla is pronounced like y for most speakers in Spain
• The stress falls on:
  • voy
  • a-TAR
  • GLO-bos
  • SI-lla

So the whole sentence sounds roughly like:

boy ah ah-TAR lohs GLO-bohs ah lah SEE-ya

Not necessarily wrong, but atar is the more neutral and widely expected choice here for a learner of Spanish from Spain.

Amarrar also means to tie / fasten, but depending on region and context it can sound less neutral or more specific. In Spain, atar is generally the safer everyday verb for this sentence.