Question

what observation led to the discovery of protons? how did we know that they were positively charged?

Answer 1

In 1886 Goldstein discovered existence of positively charged rays in the discharge tube by using perforated cathode. These rays were named as anode rays or cannal rays.

Later, Rutherford discovered alpha and beta ‘rays’ from uranium. He later demonstrated that alpha rays are the nuclei of helium atoms.

He discovered in 1914 that the nucleus of an atom constituted and extremely dense but small fraction of the volume of an atom and that this nucleus was positive in charge.

Given the discoveries of electrons in 1897 by Thomson, Rutherford and other scientists decided that a positively charged atom must exist to center the electron to create equally neutral atoms.

Thompson proposed the name ‘positive rays’. Rutherford, in 1914, suggested that this something that was positively charged or the sportive ray of Thompson was a particle.

The name proton was given to the hydrogen nucleus by Ernest Rutherford in 1920, because in previous years he had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by collision, and was thus a candidate to be a fundamental particle and building block of nitrogen, and all other heavier atomic nuclei.