balancing chemical equations

[Willis666]

I was practicing some balancing chemical equations for a chemistry test, and I noticed this:
Cu(NO3)2 (numbers are subscripts.)

I've never seen parenthesis in a chemical formula before, no clue what it means. Nothing in my text books, and I can't really ask the teacher since the test is tomorrow.

The equation was in my book, so its not going to be something I have yet to learn.

Here's the full, unbalanced equation.

Cu + AgNO3 ----> Cu(NO3)2 + Ag

Sorry if this is a really stupid question, i don't know much about chemistry (i know what i learn in class.)

[Simon Bridge]

It means that the entire molecular ion inside the parentheses appears twice, as in:

NO3- -- Cu2+ -- NO3-

[Ygggdrasil]

It basically means that there are two of the chemical species within the parentheses. Cu(NO3)2 means that the substance has two NO3- ions for every one Cu2+ ion. You could very well write this as CuN2O6, but keeping it written as Cu(NO3)2 helps to emphasize that it consists of Cu2+ and NO3- ions.

[Willis666]

Okay, thanks.

[keisu]

And also Cu(NO3)2....Cu^2+ and NO3 ^-1, remember the charges come down, so that's how you get Cu1(NO3)2