Question

3 li lithium 6.941 how many neutrons does the element lithium have? 6.9 10 4 3

Explanation:

Step1: Recall atomic number and mass - number relationship

The atomic number of lithium ($Li$) is 3 (the top - left number in the element box), and the average atomic mass is 6.941. For a neutral atom, the atomic number ($Z$) is equal to the number of protons. The mass number ($A$) is approximately the sum of protons and neutrons. Since the number of protons ($p$) is 3, and we assume the most common isotope (mass number is close to the average atomic mass rounded to the nearest whole number). Rounding 6.941 gives 7.

Step2: Calculate the number of neutrons

The formula to find the number of neutrons ($n$) is $n=A - p$. Substituting $A = 7$ and $p = 3$ into the formula, we get $n=7 - 3=4$.

Answer:

C. 4