Question

How was the atomic number discovered?

Answer 1

Protons, neutrons, and electrons are the subatomic particles of an atom. To calculate the number of protons and neutrons present in an atom, the atomic number and atomic mass of the atom are required. Here, the atomic mass and the atomic number of atoms refers to the periodic table. In the periodic table, elements are arranged with increasing order of their atomic numbers. The position of an atom or element in the periodic table gives an idea about the atomic number of an element.

Complete step by step answer:
- The atomic number is discovered by the scientist Henry Moseley. He said that the atomic number is nothing but the numbers of the protons present in an atom.
- He studied the X-ray spectra of the different elements in 1913. He got different X- frequency for different elements.
- Then he plotted the graph between the atomic number and the X-ray frequency. He found that the frequency obtained is related to the numbers of the protons present in an element. - Hence, he concluded that the atomic number of an element is equal to the numbers of the protons present in it.
- In this way, the atomic number is discovered by Henry Moseley.

Note: Atomic number represents the number of protons or electrons present in the element. The atomic number is represented by the letter Z. While the mass number is the total number of protons and neutrons present in the nucleus of an element. The mass number is represented by the letter A. The atomic number of an atom is always less than the atomic mass number of an atom.