Lets say I have a solution of NaCl and decide to add some AgNO3. I know a white precipitate will form so obviously some Ag+ ions have dropped their NO3- counterparts and combined with Cl- ions instead. Why does this happen? Is it all to do with electronegativity? Is it a simple matter of Cl- anions being more electronegative than NO3- anions and Ag+ cations being more electropositive than Na+ cations?