One isotope of sodium has 11 protons and 7 neutrons. What is the mass number of this isotope?

Gallium has an atomic mass of 69.723 amu. The Ga-69 isotope (68.926 amu) is 60.11% abundant. What is the mass (amu) of the other isotope?

Gallium has two naturally occurring isotopes: Ga-69 with a mass of 68.9256 amu and a natural abundance of 60.11%, and Ga-71. If the atomic mass of gallium is 69.723 amu, what is the mass of Ga-71?

A sample of chlorine weighing 20.57 grams contains two naturally occurring isotopes: Cl-35 and Cl-37. If the atomic masses are 34.9689 amu for Cl-35 and 36.9659 amu for Cl-37, and the natural abundance of Cl-35 is approximately 75.78%, what is the mass of Cl-35 in the sample?

Which formula is used to calculate the percentage abundance of an isotope in a sample?

How many neutrons does a typical lithium atom have?

How many neutrons are present in the most common isotope of potassium (K-39)?

Which of these refers to atoms with the same atomic number but different atomic masses?

How many neutrons are present in an atom of potassium-39?