## General Properties of Nucleus:

**(1) Atomic Number (Z)-** It represents the total number of protons inside the nucleus.

**(2) Mass Number (A)-** It represents the total number of protons and neutrons inside the nucleus.

**(3) Nuclear Mass-** It is expressed in terms of atomic mass unit (amu). One amu is defined as 1/12th mass of C^{12} i.e. there are 6.025 x 10^{26} atoms in 1 kg mole (or 12 kg) of carbon.

**(4) Nuclear Charge-** The charge of the nucleus is positive due to protons contained in it.

Charge of proton = 1.6 x 10^{-19} C |

(5) **Nuclear Size-** Nuclear radius is of the order of 10^{-15} m. According to the semi-empirical formula, the nuclear radius is given by-

R = R_{0} A^{1/3}Where R _{0} is the constant with an average value of 1.4 x 10^{-15} m. |

(6) **Nuclear Shape-** In order to provide the least surface area, the nucleus is always spherical in shape.

(7) **Nuclear Density-**

**(8) Nuclear Spin and Quantum States-**Similar to electrons, nucleons also possess a spin. Also, there are sets of quantum states and a corresponding number of discrete energy levels with nucleons. Transitions between different nuclear states are accompanied by the emission of γ-rays.

(9) **Nuclear Stability-** Nuclear stability means that the nucleus of an element is stable and thus it does not decay spontaneously emitting any kind of radioactivity.

**Factors affecting nuclear stability are-**

(i) **Number of Protons and Neutrons-** If the N/Z ratio is one, nuclei are more stable and if N/Z > 1.5, nuclei are unstable.

Also for an even number of protons and neutrons, nuclei are in general stable than those having an odd number of them.

(ii) **Binding Energy-** Intermediate elements with comparatively large binding energy per nucleon are more stable than lighter and heavier elements.

(iii) **Nuclear Forces-** According to ** Yukawa Meson’s theory**, nuclear forces arise due to the rapid exchange of π-mesons (π

^{+}, π

^{0}and π

^{–}) between protons and neutrons.

Nuclear forces are short-range, attractive forces which are strongest in nature for P-P, P-N and N-N interactions. These forces are independent of charge.

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