Two or more nuclides are iso tones, if they have the same neutron number. Hence,
(a) ${ }_{8} O ^{16}=8$ protons $+8$ neutrons
(b) ${ }_{7} N ^{15}=7$ protons $+8$ neutrons
(c) ${ }_{6} C ^{14}=6$ protons $+8$ neutrons
(d) $_{13} Al ^{27}=13$ protons $+14$ neutrons
(e) ${ }_{9} F ^{17}=9$ protons $+8$ neutrons