Answer:
The pair co,Ni is out of order in terms of atomic mass
Explanation:
For co,Ni
Atomic mass of Co = 58.9331 u
Atomic mass of Ni = 58.6934
For Li,be
Atomic mass of Li = 6.941 u
Atomic mass of be = 9.012182 u
For I,xe
Atomic mass of I = 126.90447 u
Atomic mass of Xe = 131.293 u
Hence, the pair co,Ni is out of order in terms of atomic mass
