contestada

What is the total number of protons in the nucleus of an atom of potassium-42?
(1) 15 (3) 39
(2) 19 (4) 42

Respuesta :

The answer is (2) 19. The number of protons of any isotope of a given element is just its atomic number (because the number of protons identifies the element). Potassium's atomic number is 19.