The nucleus of which chemical element contains 19 protons 1-potassium 2-sulfur 3-fluoro4-argon.

From the theory of the structure of the atom, we remember that an atom consists of a positive nucleus and negative electrons. The nucleus consists of positively charged protons and neutral neutrons. So the charge of the nucleus corresponds to the total charge of the protons in it. The number of electrons in an atom is equal to the number of protons in the nucleus. Therefore, an element with 19 protons will have 19 electrons.

In the periodic table, the ordinal number of chemical elements corresponds to the total number of electrons. This means that our required element will have number 19. In the periodic table, the element with this number is potassium.

Answer: 19 protons are contained in the nucleus of the potassium atom.