Question

how many neutrons are in a lithium atom?

Explanation:

Step1: Find the atomic number and mass number of lithium

The atomic number ($Z$) of lithium is $3$ (from the periodic table). The most common isotope of lithium has a mass number ($A$) of $7$.

Step2: Use the formula for the number of neutrons

The formula for the number of neutrons ($N$) is $N = A - Z$.
Substitute $A = 7$ and $Z = 3$ into the formula: $N=7 - 3$.

Answer:

$4$