When the valence electrons form a covalent bond, they DE-LOCALIZE from their atom. They begin belonging to both atoms that form the covalent bond. ... This is in contrast with the ionic bond, where each atom gives or receives the valence electrons (which transform the atoms into ions) thus forming the ionic bond.
Nickel-62 has the highest binding energy per nucleon of any isotope for any element. Isotopes heavier than 62Ni cannot be formed by nuclear fusion without losing energy.
