The isotope of an atom containing 31 protons and 39 neutrons suddenly has two neutrons added to it. What isotope is created?
Yttrium-72

Gallium-72

Gallium-41

Yttrium-41

Gallium-72

Explanation:

The elements are identified by the number of protons of the atom, which is its atomic number.

In this case the number of protons 39 (atomic number 39) permit you to identify the element as gallium.

Now, to identify the isotope you tell the name of the element and add the mass number.

The mass number is the sum of the protons and the neutrons

In this case, the number of neutrons is the original 39 plus the 2 added suddenly, i.e. 39 + 2 = 41, so the mass number is 31 + 41 = 72

Therefore, the isotope is gallium - 72.

every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. therefore, there must be the same number of atoms of each element on each side of a chemical equation.