PHASES PHASE 1 STRUCTURE OF ATOM PHASE 2 BINDING ENERGY AND MASS DEFECT PHASE 3 NATURAL RADIOACTIVITY, ARTIFICIAL RADIOACTIVITY & NEUTRON BOMBARDMENT. PHASE 4 FISSION AND FUSION. PHASE 5 CHAIN REACTION,CRITICAL MASS AND REFLECTORS.
SCOPE TO FAMILIARISE YOU WITH THE STRUCTURE OF ATOM, BINDING ENERGY AND MASS DEFECT, NATURAL AND ARTIFICIAL RADIO ACTIVITY,FISSION, FUSION, CHAIN REACTION, CRITICAL MASS AND REFLECTORS.
ELEMENT AN ELEMENT IS A SUBSTANCE WHICH CANNOT BE SPLIT UP INTO TWO OR MORE SIMPLER SUBSTANCES BY THE USUAL CHEM METHODS OF APPLYING HEAT, LT OR ELECTRIC ENERGY. AN ELEMENT IS MADE UP OF ATOMS, ALL HAVING SAME ATOMIC NUMBER.
A MOLECULE IS THE SMALLEST PARTICLE OF A SUBSTANCE ( ELEMENT OR COMPOUND) WHICH HAS THE PROPERTIES OF THAT SUBSTANCE AND CAN EXIST IN FREE STATE. MOLECULE
AN ATOM CAN BE DEFINED AS THE SMALLEST QUANTITY OF AN ELEMENT WHICH CAN ENTER INTO A CHEMICAL REACTION. ALL ATOMS OF A PARTICULAR ELEMENT ARE CHEMICALLY ALIKE BUT THEY DIFFER FROM THE ATOMS OF OTHER ELEMENTS.
ALBERT EINSTEIN PROPOUNDED MASS AND ENERGY ARE CONVERTIBLE AND EST THE FORMULA : E = mc 2
WHERE, E = energy in ergs, m = mass in grams,
c = velocity of lt (3 x 10 10 cmsec)
NEUTRONS BEING ELECTRICALLY NEUTRAL, CAN PENETRATE UPTO NUCLEUS OF AN ATOM AND LIKELY TO CAUSE BREAKING UP OF NUCLEUS.
IN BEAKING UP OF AN ATOM, THERE IS CHANGE IN TOTAL MASS AND THE ENERGY THUS RELEASED IS ENORMOUS.
EINSTEIN'S MASS ENERGY RELATIONSHIP E = MC 2 E = ENERGY IN ERGS – (10 7 ERGS = 1 JOULE ) M = MASS IN GRAMS C = VELOCITY OF LIGHT = 3 x 10 10 CM/SEC ERG - WORK DONE BY A FORCE OF 1 DYNE WHEN ITS POINT OF APPLICATION MOVES BY ONE CM IN THE DIRECTION OF THE FORCE.
BINDING ENERGY IS THAT AMT OF ENERGY WHICH WOULD NEED TO BE APPLIED TO A NUCLEUS TO BREAK IT DOWN INTO ITS CONSTITUENT NUCLEONS “STABILITY OF NUCLEUS CAN BE ASSESSED FROM THE VALUE OF ITS BINDING ENERGY PER NUCLEON. GREATER THE ENERGY PER NUCLEON, GREATER IS THE STABILITY”
BINDING ENERGIES PER NUCLEON 20 40 60 80 100 120 140 160 180 200 220 240 9 8 7 6 5 4 3 2 1 0 U 235 2 H 1 2 H 1 6 L1 3 10 B 5 MAX 8.7 MEV E N E R G Y (MeV ) MASS NO
IF AN ORBITING ELECTRON IS PULLED OR FORCED AWAY FROM AN ATOM, THE ATOM, NOW POSITIVELY CHARGED, IS CALLED A POSITIVE ION AND THE PROCESS IS KNOWN AS IONISATION.THE DETACHED ELECTRON OFTEN ATTACHES ITSELF TEMPORARILY TO ANOTHER ATOM WHICH IS THEN A NEGATIVE ION.
COMPARATIVELY LONGER RANGES. – 60” (AIR), 4 MM (AL)
Gamma rays, or high energy photons, are emitted from the nucleus of an atom when it undergoes radioactive decay. The energy of the gamma ray accounts for the difference in energy between the original nucleus and the decay products. Gamma rays typically can have about the same energy as a high energy X ray. Each radioactive isotope has a characteristic gamma-ray energy. GAMMA RAYS
The emission of electrons from matter by EM radn of certain energies. The energy of the incident radn is tfr in discrete amts (photons) each of magnitude hy. Each photon absorbed will eject an electron provided that the photon energy exceeds a certain value -- the wk function. The max KE of the electrons E is then given by E = hv – . This is known as Einstein’s Photo electric theory.
HALF - LIFE The time taken by half of the atoms of a RA element to disintegrate is called its half life. After half life, the radioactivity of an element also becomes half of the original value. The half life of Ra is about 1600 yrs, which means that a given sample of Ra will disintegrate half in 1600 yrs. Eg, if we start with 1 gm of Ra today, then half gm of it will disintegrate in 1600 yrs. After another 1600 yrs half of remains will have disintegrated and so on.
AIR – Oxygen and Nitrogen little or no significance.
SOIL– Na 24- half life about 15 hrs, emits Beta and Gamma of nearly 3 MeV. Mn essential for plant growth capture and produce Mn 56 , half life 2.6 hrs, emits Beta and gamma. Silicon and Al produce silicon 31 (2.6 hrs) and Al 28 (2.5 mins). Although contribute to the imdt activity, would be of no significance of after an hr or so.
FISSION IS A PROCESS , THE REACTING NUCLEUS SPLITS INTO PARTS OF ROUGHLY EQUAL MASS, BOTH OF WHICH HAVE MUCH LOWER ATOMIC NOS AND MASS NOS THAN THE ORIGINAL NUCLEUS. THE REACTION IS ACCOMPANIED BY THE RELEASE OF ENORMOUS QTY OF ENERGY AND VERY IMP, THE EXPULSION OF ONE OR MORE NEUTRONS.
THE COMBINATION OF VERY LIGHT NUCLEI, LOW IN MASS NUMBER INTO PRODUCT NUCLEI THAT ARE NEARER THE MIDDLE OF SCALE, FORMS THE FUSION PROCESS.
( BECAUSE THE FIRST THOUGHTS IN THIS FIELD WERE DIRECTED TOWARDS THE USE OF THE LIGHTEST OF ALL NUCLEI HYDROGEN, THE EARLIEST EXPLOSIONS PRODUCTED BY THIS MEANS WERE POPULARLY TERMED HYDROGEN EXPLOSIONS)