An ionic bond is a bond that forms between Olons with opposite charges.
O Atoms with neutral charges.
O One atom's nucleus and another atom's electrons
O The protons of different atoms

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf   

Aquantity of that isotope to decay to 1/2 of  its original value