Question

how many neutrons are in a ⁴he atom? answer: a 0 b 2 c 4 d 6

Explanation:

Step1: Recall atomic number and mass - number relationship

The notation $^4He$ means the mass - number $A = 4$. Helium has an atomic number $Z=2$. The number of neutrons $N$ is given by the formula $N=A - Z$.

Step2: Calculate number of neutrons

Substitute $A = 4$ and $Z = 2$ into the formula $N=A - Z$. So $N=4 - 2=2$.

Answer:

B. 2