An atom has a mass number of 25 and 13 neutrons. What is the atomic number of this atom?
Answer:
The atomic number is \(12,\) which is the atomic number for magnesium.
Explanation:
The mass number of an isotope is the sum of the protons and neutrons in its atomic nuclei.
If we know the mass number \((A)\) and the number of neutrons \((N)\), we can calculate the atomic number \((Z)\) by subtracting the number of neutrons from the mass number.
\(\mathrm{A}-\mathrm{N}=\mathrm{Z}\)
\(25-13=12\)
The atomic number of the element is \(12.\) Atomic number is the number of protons in the nuclei of all atoms of an element. The element with the atomic number 12 is magnesium.
This is \({ }^{25} \mathrm{Mg},\) or magnesium-25, which can be abbreviated as Mg-25.