Question

question 1 of 10
na - 23 has 12 neutrons. what is its atomic number?
a. 11
b. 12
c. 23
d. 34

Explanation:

Step1: Recall atomic mass formula

Atomic mass = Protons + Neutrons. For Na - 23, atomic mass is 23.

Step2: Calculate number of protons

Let the number of protons be $p$. We know atomic mass = 23 and neutrons = 12. So $p+12 = 23$, then $p=23 - 12$.

Step3: Determine atomic number

Atomic number is equal to the number of protons. $p = 11$.

Answer:

A. 11