Question

A cobalt atom has 27 protons. What number of neutrons would make a cobaltatom most stable?OA. 54OB. 27OC. 25OD. 32

Answer 1

D. 32.

Step-by-step explanation:

Remember the formula of atomic mass:

`atomic\text{ mass=atomic number+\# neutrons.}`

If you go to see the periodic table, you can note that the atomic mass of cobalt is 58.9 amu rounded to 59 amu. Let's solve for '# neutrons' and replace the atomic mass (59) and the atomic number (27) (remember that the number of protons is the same that the atomic number), like this:

`\begin{gathered} #\text{ neutrons=atomic mass-atomic number,} \\ #\text{ neutrons=59-27,} \\ #\text{ neutrons=32.} \end{gathered}`

The answer would be that the number of neutrons to make a cobalt atom most stable is D. 32.