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Some properties of the atomic nuclei:

• Any atom is composed of the atomic nucleus, around which electrons are orbiting in elliptical shells.So, in a neutral atom the number of the protons in the nucleus equals the number of the orbital electrons.From these data the atomic mass is concentrated in the atomic nucleus, and the nuclear density is, approximately, constant and equals 1017 kg/m3 (about 100 millions ton/cm3).- The number of the protons in a nucleus is called its atomic number Z, while the total number of protons and neutrons, in it, is called the mass number A. So the number of neutrons N in a nucleus is N = A - Z. Symbolically, any atom is represented by the first letter written in capital, or by the first one in capital and other one written in small.- The nucleus of any element is composed of the same number of protons Z, but it may have different numbers of neutrons N. these 8

different forms of the same element are called isotopes of the elemen

Some properties of the atomic nuclei:

• Any atom is composed of the atomic nucleus, around which electrons are orbiting in elliptical shells.


• The radius of the atom is in the order of 10-10 m, while the radius of the nucleus is in the order of 10-15 m, so that the volume of the nucleus is smaller than that of atom by about thousand trillions times (trillion = 1012). Due to these dimensions, the atom is similar to the solar system, with its inter- planetary distances.


• Any atomic nucleus consists of nucleons, which are protons or neutrons. The proton mass is, approximately, higher than that of the electron by about 1836 times, while the neutron mass is higher by about 1838 times. So, the neutron and the proton may be considered as particles with the same mass. From these data the atomic mass is concentrated in the atomic nucleus, and the nuclear density is, approximately, constant and equals 1017 kg/m3 (about 100 millions ton/cm3).


• The charge of the proton equals to the electron charge in magnitude (1.6x10-19 Coulomb), but it is positive in sign, while the neutron is neutral (e.g. its total charge equals zero). So, in a neutral atom the number of the protons in the nucleus equals the number of the orbital electrons.


• The number of the protons in a nucleus is called its atomic number Z, while the total number of protons and neutrons, in it, is called the mass number A. So the number of neutrons N in a nucleus is N = A – Z. Symbolically, any atom is represented by the first letter written in capital, or by the first one in capital and other one written in small. The atomic number is written in the lower left corner, while the
  mass number is written in the upper left one. Example of that is 12C (or 6
  carbon-12), 35Cl (or chlorine-35), 51Cr (chrome-51) and 114Cd (or 17 23 48
  cadmium-114).


• The nucleus of any element is composed of the same number of protons Z, but it may have different numbers of neutrons N. these
  8

different forms of the same element are called isotopes of the elemen