Question

how many neutrons are there in 226ra? 226ra 88 314 226 138

Explanation:

Step1: Recall atomic number of Ra

Radium (Ra) has an atomic number of 88.

Step2: Use neutron - mass number relation

The number of neutrons $N$ is calculated by subtracting the atomic number $Z$ from the mass number $A$. For $^{226}Ra$, $A = 226$ and $Z=88$. So $N=A - Z$.
$N=226 - 88$
$N = 138$

Answer:

D. 138