Mrs. Eleanor Roosevelt, (United States) holding a Declaration of Human Rights. Â© UN Photo. The formal inception of Human Rights Day dates from 1950, after the Assembly passed resolution 423 (V) inviting all States and interested organizations to adopt 10 December of each year as Human Rights Day.he formal inception of Human Rights Day dates from 1950, after the Assembly passed resolution 423 (V) inviting all States and interested organizations to adopt 10 December of each year as Human Rights Day.
The number of protons in the nucleus of the atom is equal to the atomic number (Z). The number of electrons in a neutral atom is equal to the number of protons. The mass number of the atom (M) is equal to the sum of the number of protons and neutrons in the nucleus. The number of neutrons is equal to the difference between the mass number of the atom (M) and the atomic number (Z).
In a given element, the number of neutrons can be different from each other, while the number of protons is not. These different versions of the same element are called isotopes. Isotopes are atoms with the same number of protons but that have a different number of neutrons. Since the atomic number is equal to the number of protons and the atomic mass is the sum of protons and neutrons, we can also say that isotopes are elements with the same atomic number but different mass numbers.