Problem using subjunctive mood in different tenses

Question

How are these sentences translated this in Italian? I am having problem using the congiuntivo.

If I had asked it later, she wouldn't have accepted it.

If I had her number I would call her.

If I had had her number I would have called her.

Answer 1

I would translate the example sentences as follows:

Se l'avessi chiesto dopo, non avrebbe accettato

Se avessi il suo numero, la chiamerei

Se avessi avuto il suo numero, l'avrei chiamata

This kind of sentences are called periodi ipotetici (hypotetical sentences) in Italian. An exposition of the rules about them can be found here. Let me briefly summarize them for you in your examples.

If I had asked it later, she wouldn't have accepted

In English, this is what's called a type 3 conditional sentence, because it describes an unreal past condition and its probable result in the past. In Italian the corresponding version is a periodo ipotetico dell'irrealtà (unreal hypotetical sentece), in the past form. It requires the if clause (protasi in Italian) at the congiuntivo trapassato and the main clause (apodosi in Italian) at the condizionale passato. So

Se l'avessi chiesto dopo, non avrebbe accettato

If I had her number, I would call her

In English this is a type 2 conditional sentence, because it describes an hypothetical condition, and its probable result. The corresponding Italian version is the periodo ipotetico della possibilità. It requires the if clause at the congiuntivo imperfetto and the main clause at the condizionale presente or imperativo. So

Se avessi il suo numero, la chiamerei

If I had had her number, I would have called her

This is again a type 3 conditional sentence. As such, it is translated with a periodo ipotetico dell'irrealtà, set in the past.

Se avessi avuto il suo numero, l'avrei chiamata

To summarize

 Type of periodo ipotetico | If clause (protasi)     | Main clause (apodosi)
------------------------------------------------------------------------------
   Realtà                  | Indicativo              | Indicativo/Imperativo
   (the hypothesis is      |                         |
    certain or very        |                         |
    likely)                |                         |
------------------------------------------------------------------------------
   Possibilità             | Congiuntivo imperfetto  | Condizionale presente/
   (the hypothesis is      |                         | Imperativo
    possible but not       |                         |
    certain)               |                         | 
------------------------------------------------------------------------------
    Irrealtà, I            | Congiuntivo imperfetto  | Condizionale presente/
    (the hypothesis is     |                         | Imperativo
     impossible and set    |                         |
     in the present)       |                         |
------------------------------------------------------------------------------
    Irrealtà, II           | Congiuntivo trapassato  | Condizionale passato
    (the hypothesis is     |                         | 
     impossible and set    |                         |
     in the past)          |                         |
------------------------------------------------------------------------------

By the way, I never really understood the difference between Possibilità and Irrealtà I. Thankfully they have the same tenses, so I can happily ignore their distinction. Note that in English they are both conflated into a type 2 conditional clause.