Na-23 has 12 neutrons. What is it’s atomic number?

11

Explanation:

Data obtained from the question include:

Mass number = 23

Neutron = 12

Atomic number =.?

Next, we shall determine the number of protons present in the element.

This can be achieved by doing the following:

Mass number = Proton + Neutron

Mass number = 23

Neutron = 12

Proton =...?

Mass number = Proton + Neutron

23 = Proton + 12

Collect like terms

Proton = 23 – 12

Proton = 11

The atomic number of an element is equal to the proton number.

Atomic number = proton number

Proton number = 11

Atomic number = proton = 11

Therefore, the atomic number is 11.