Two nuclides are isotones if they have the same neutron number N, but different proton number Z. For example, boron-12 and carbon-13 nuclei both contain 7 neutrons, and so are isotones. Ionic bonding is the electrostatic force of attraction between positively and negatively charged ions. These ions have been produced as a result of a transfer of electrons between two atoms with a large difference in electronegativities.