# How many protons, electrons and neutrons are present in an atom of potassium with a mass number of 39. ..?

How many protons, electrons and neutrons are present in an atom of potassium with a mass number of 39 and charge of +1?

19 protons, 19 neutrons, 19 electrons

19 protons, 20 neutrons, 18 electrons

19 protons, 39 neutrons, 19 electrons

39 protons, 18 neutrons, 18 electrons

Relevance

the second one

• 19 protons because Potassium's atomic number is 19. 39-19=20 neutrons and 18 electrons because it has lost an electron.

19 protons, 20 neutrons, 18 electrons

• Use a periodic table. Iodine is element number 53, and this indicates how many protons are present. Since the atom is neutral, there are just as many electrons as protons. Now since 125 is the total atomic weight, that indicates that 125-53 gives the leftover mass, which is the neutrons. Use this same process for the rest.

• 19 p, 20 n, 19e because u have to have the same number of protons and electrons otherwise it is an ion and the only way to get molecular weight of 39 is adding the p and n together so u do the math...39-19=? (Hint:20)