3. Nuclear Chemistry Flashcards
Henri Becquerel (1896)
-exposed uranium salts to sunlight and it phosphorescent (umilaw nang slight beh). Placed glowing salts on photographic plate (then coins inbetween salt and plate) ➡️ photographic images of coin
-salts emitting something else other than visible light, akin to xrays
-noble prize shared with marie and pierre curie
Alpha particles
-Helium nuclei; two protons and two neutrons (+2)
Beta particles
-electrons; (-1)
Gamma rays
-high energy electromagnetic radiation; no mass or charge
Cosmic rays
Only radiation known to have even higher frequency and energy than gamma rays
Wavelength
-distance from one crest to next
-only difference between one form of electromagnetic radiation and another
Frequency, wavelength and energy
⬆️Frequency ⬆️Energy ⬇️Wavelength
Photons
-smallest unit of packets of electromagnetic radiation
Radioactive
-materials that emit radiation(alpha, beta, gamma)
-radioactivity comes from the atomic nucleus
Radioactive isotope
-radiation emitting isotope of an element
-some isotopes are radioactive, some are not
(i.e. hydrogen & deuterium (stable); tritium (radioactive))
Nuclear reaction
-reaction that changes atomic nuclei of elements
•LIGHTER ELEMENTS: stability occurs when number of protons and neutrons are approximately equal.
•HEAVIER ELEMENTS: stability requires more neutrons than protons
Beta Emission
-if a nucleus has more neutrons than it needs, it can stabilize by converting a NEUTRON ➡️ PROTON + ELECTRON
-proton remains but ELECTRON is EMITTED (beta particle)
Transmutation
-changing of one element into another
-happens naturally when element gives off beta particle
Alpha emission
-mostly occuring for HEAVY ELEMENTS like polonium
-new nucleus always has a mass number four units lower and atomic number two units lower than original nucleus.
Positron Emission
-positive electron (0 mass, +1 charge)
-rarer than beta and alpha emission
-nucleus is transmuted to another nucleus with SAME MASS NUMBER but an ATOMIC NUMBER LESS THAN 1.
Gamma emission
-often accompanies alpha and beta emissions
-if pure gamma emission, no change in atomic mass and number
-high energy (excited) state ➡️ lower energy (more stable)
-removes excess energy
Electron capture
-extranuclear electron is captured by the nucleus and it reacts with proton to form neutron
(Ung other four puro decomposition, ito lng yung parang combination)
When nucleus gives off radiation…
It decays
Half life
Time it takes for one half of any sample of radioactive material to decay
Some radioactive nuclei half life
HYDROGEN-3 (TRITIUM)
12.26 yrs
Some radioactive nuclei half life
CARBON-14
5730 yrs
Radioactive dating
-technique used to date archeological objects as old as 60,000 yrs
-relies on the principle of carbon-12/ carbon-14 ratio of an organism that it remains constant during lifetime
-when an organism dies, carbon-12 level remains constant since it is stable but carbon-14 decays by beta emission
*Remember!!
Usually around 13.7 disintegrations/min-gramC ang Carbon-14 right after mamatay organism, use this as basis (if di given)
Ionizing radiation
-alpha, beta, gamma, positron, xrays
-because when they interact with matter, they usually knock out electrons, creating positively charge ions from neutral atoms
IONIZING RADIATION CHARACTERISTICS
1. Intensity
-Number of particles or photons emerging per unit time
-Common units: Becquerel, Bq (SI; 1 disinteg/sec) and Curie, Ci (3.7x10^10 disinteg/sec; Basis Radium)
-Intensity inverse to distance from radiation source
Measured by:
•Geiger-Muller counter (imagine shape ng resistor hahahaha) and proportional counter containing He/ Ar
-when alpha/ beta/ gamma are emitted, they ionize gas inside the instrument. Instrument detects electric current passing b/w two electrodes.
•Scintillation counter
-have phosphor that emits a unit of light for each particle/ ray that strikes it. Counts/time unit
IONIZING RADIATION CHARACTERISTICS
2. Energy
-Penetrating power of radiation depends on energy and mass of particles
•Alpha-most massive, most highly charges, least penetrating; stopped by paper, clothing, skin
•Beta-less mass, lower charge, greater penetrating power
•Gamma- have neither mass nor charge, greates penetrating power
Activity of radiation
Same as intensity of radiation
EFFECTS OF RADIATION ON BODY
1. Roentgen, R
-measure of energy delivered by radiation source
- 1R = 2.58x10^-4 coulomb of ions/kg
-does not take into account the effect of radiation on tissue and the fact that different tissue absorb different amounts of delivered radiation
EFFECTS OF RADIATION ON BODY
2. Rad (Radiation Absorbed Dose)
-measure of radiation absorbed from source
-SI unit: Gray (Gy); 1Gy = 100 rad
-ratio between radiation absorbed by tissue and radiation delivered to tissue
EFFECTS OF RADIATION ON BODY
3. Rem (Roentgen Equivalent for Man)
-measure effect of radiation shen a person aborbs 1 roentgen
-SI unit: Sievert (1Sv=100 rem)
-Tissue damage from 1 rad of absorbed energy depends on type of radiation
-ratio between the tissue damage caused by a rad of radiation and type of radiation
Damage on organisms part 1:
-Alpha: least penetrative but causes most damage. But since they cannot pass through skin, considered as least harmful
-Gamma: most penetrative so considered as most dangerous and harmful form of radiation.
-Beta: always inbetween alpha and gamma
*For comparison purposes, determine equivalent dose (rem). If different sources, summed up in rems
Damage on organisms part 2:
Harm may arise in 2 ways:
1. Small doses of radioactivity over a period of years can cause cancer (i.e. tanning overexposure to UV radiation, skin cancer)
- Form of radiation strikes egg or sperm cell, causes changes in genes (mutation)
Background radiation
-Naturally occuring radiation (i.e. cosmic rays, terrestrial radiation like rocks, inside human body like K-40 and Ra-266, Ra in air)
-Mas marami pa nga naturally occuring radiation kesa artificial radiation (normally ah)
Nuclear medicine
Use of radioactive isotopes as tools for both diagnosis and treatment of diseases
Medical imaging
-most widely used in nuclear medicine
-create a picture of target tissue
-injects pure radioactive element in target tissue
-method of radiation detection and data passes to computer (intensity and location data)
-i.e. Magnetic Resonance Imaging (MRI)
Radioactive Therapy
-selective destruction of pathological cells and tissues (remember gamma rays, xrays, etc are deteimental to cells)
-ionizing radiation damage cells, especially those divide rapidly (i.e. radiation in cancer cells)
Nuclear Fusion
-joining together atomic nuclei to form a nucleus heavier than starting nuclei)
-reactions in sum, hydrogen bomb
Transuranium elements
-elements with atomic number greater than 92
-artificial; prepared by fusion process; heavy nuclei bombarded with light ones
-short half lives since super unstable
Nuclear fission
-Enrico Fermi, Otto Hahn, Lisa Meitner
-bombarded uranium-235 with neutrons
-results to fragmentation of large nuclei into smaller pieces
-most important product of decay: atomic energy
-each fission produces 3 neutrons; chain reaction
Nuclear power plant
-nuclear fission
-energy produced is sent to heat exchangers and used to generate steam, drives turbine, produces electricity
-problem:
•waste disposal, highly radioactive and long half lives
•site not guaranteed to stay dry for centuries; moisture may corrode steel cylinders containing nuclear waste
