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CP Sci 9- 1st Sem.

Gen Chem - 1st Sem.

Changes in the Nucleus: (3-4)


    1.    Describe the changes that accompany nuclear reactions.

    2.    Define radioactivity.

Key Terms:

    nuclear reaction    strong nuclear force    radioactive decay    nuclear equation

Web Resources:

Nuclear Stability:

Nearly all atoms that you come in contact with in you daily life are stable.  In other words, they are not radioactive.  Although the nucleus is crowded with like charges, the protons do not repel each other.  They are held together by a strong nuclear force.  This strong nuclear force is increased by the addition of the neutral neutron (no repulsive force). 

bulletAtoms with atomic numbers 1-20 are stable with the equal numbers of neutrons and protons
bulletAbove atomic number 20, increasing amounts of neutrons are required to stabilize the nucleus
bulletAt atomic number 83, no amount of neutrons can make the atom stable - all are radioactive
bulletAdding extra neutrons can also make an atom radioactive

Types of Radioactive Decay:

1)    Alpha

bulletConsists of 2 protons & 2 Neutrons - identical to Helium
bulletLow penetrating power - easily stopped by paper or clothing
bulletCan travel only a few centimeters through the air
bulletDo not pose a health hazard

alpha decay


2)    Beta

bulletConsists of a high speed electron
bulletThe electron is formed in the nucleus when a neutron is converted into a proton and a high speed electron
bulletHas essentially no mass
bulletAbout 100 times more penetrating than the alpha particle
bulletCan pass through clothing and damage skin

beta minus decay

3)    Gamma

bulletEnergetic form of light similar to X-ray
bulletHave no mass
bulletAccompany alpha and beta radiation
bulletCan travel through tissue and solid material - stopped by concrete and lead

gamma decay



Last modified: September 05, 2004