Answer: Ne ( Neon )
Explanation: Lithium ( Li ), beryllium ( Be ), carbon ( C ), oxygen ( O ), and neon ( Ne ), are all in Period 2 in that order. Sodium ( Na ) is in Period 3. Since electron affinities decrease as you go down, Na would have a lower electron affinity level then Li but since electron affinities increase as you go across a period, only neon is farther right then oxygen ( O ), so it would be the only one element of this group that would have a higher electron affinity than that of oxygen.
