Question

question 1 of 30
a cobalt atom has 27 protons. what number of neutrons would make a cobalt atom most stable?

a. 25
b. 54
c. 32
d. 27

Explanation:

Step1: Recall Cobalt's Atomic Mass

Cobalt has an atomic mass (mass number) of approximately 59. The mass number ($A$) is the sum of protons ($Z$) and neutrons ($N$), so $A = Z + N$.

Step2: Calculate Neutrons

Given $Z = 27$ (protons), solve for $N$: $N = A - Z$. Using $A \approx 59$, $N = 59 - 27 = 32$. Also, stable nuclei often have a neutron - proton ratio close to 1 for light elements, but for cobalt (atomic number 27, a transition metal), the stable isotope has around 32 neutrons. Checking the options, 32 is option C.

Answer:

C. 32