One isotope of a metallic element has the mass number 63 and 33 neutrons in the nucleus. the cation derived from the isotope has 28 electrons.

Given

Mass number of isotope = 63

Number of neutrons = 33

So number of protons = 63 - 33 = 30

Hence atomic number of metal = 30

thus metal is = zinc

now as it is forming cation with 28 electrons it means it has lost two electrons so it must have a dipositive charge

the symbol of metal ion will be

Zn^+2

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.