Which represents the balanced nuclear equation for the beta minus decay of Co-60?

₂₇⁶⁰Co ⇒ ₂₈⁶⁰Ni + ₋₁⁰e

Given

the beta minus decay of Co-60

Required

The reaction

Solution

Radioactivity is the process of unstable isotopes to stable isotopes by decay, by emitting certain particles,  

Beta minus : ₋₁e⁰ particles

so the reaction :

Co-60 ⇒ X + beta minus

₂₇⁶⁰Co ⇒ X + ₋₁⁰e

In a nuclear decay reaction, the mass number and atomic number of the left (reactant / decayed) and right (product) sides will be the same

mass number = constant = 60

atomic number = 27 - (- 1) = 28

So the element X = ₂₈⁶⁰Ni

₂₇⁶⁰Co ⇒ ₂₈⁶⁰Ni + ₋₁⁰e

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

c) should be the answer.