Many theories regarding the structure of the atom have been proposed over the course of time. Which of the following persons first suggested that the nucleus contains positively charged protons?

Ernest Rutherford.

Explanation:

Ernest Rutherford was a British physicist and one of the greatest experimentalists. He "gave birth" to nuclear physics. He lived from 1871 to 1937.

In 1911, he performed many experiments in order to discover and explore radioactivity. In one of his experiments he discovered that the atom has a positive center charge that contains most of atom's mass. He called that nucleus the proton, after the greek word "protos" which means "first". Different number of protons can be found in the atoms of different elements, which gave their nuclei different charges. That is how he established that the hydrogen nucleus was an elementary particle.