.A pH meter is divided into two. The numbers that are lesser than 7 are the pH numbers of acids. The lesser the number, the stronger is the acid. Further, the numbers greater than 7 are for the bases and the stronger the base, the higher is the value for the pH. Thus, the answer to this item is the fourth choice, strong base.
I believe this nuclide is potassium with the symbol K. Atomic number for an element remains constant no matter how the mass changes. From the periodic table, potassium has an atomic number of 19.
