Question

question 9 of 10
which nucleus completes the following equation?
$_{92}^{226}u\
ightarrow_{2}^{4}he +?$
a. $_{92}^{222}u$
b. $_{90}^{228}th$
c. $_{90}^{222}th$
d. $_{94}^{230}pu$

Explanation:

Step1: Apply conservation of mass - number

The mass - number of uranium ($^{226}_{92}U$) is 226 and that of helium ($^{4}_{2}He$) is 4. Let the mass - number of the unknown nucleus be $A$. Then $226=4 + A$, so $A = 226 - 4=222$.

Step2: Apply conservation of atomic - number

The atomic - number of uranium is 92 and that of helium is 2. Let the atomic - number of the unknown nucleus be $Z$. Then $92=2 + Z$, so $Z = 92 - 2 = 90$.

Step3: Identify the element

The element with atomic - number 90 is thorium (Th). So the nucleus is $^{222}_{90}Th$.

Answer:

C. $^{222}_{90}Th$