Question

9 how many neutrons are in li(lithium)? assume that the mass is 7. 10 what is the best answer for the below picture?

Explanation:

Step1: Recall atomic number of lithium

The atomic number of lithium (Li) is 3, which means it has 3 protons.

Step2: Use mass - proton relationship

The mass number is the sum of protons and neutrons. Given mass number $A = 7$ and number of protons $p=3$. Let the number of neutrons be $n$. Then $A=p + n$. So $n=A - p$.

Step3: Calculate number of neutrons

Substitute $A = 7$ and $p = 3$ into the formula $n=A - p$. We get $n=7 - 3=4$.

Answer:

4