1/2. Reciprocal is the term inverted so 2 over 1 becomes 1 over 2
The reciprocal of any integer n is equal to 1/n. In this instance, the reciprocal of 2 is equal to 1/2 or one half.
2½ = 5/2 so reciprocal = 2/5
2 and 1/2 would be 5/2 the reciprocal of 5/2 would be 2/5