2Chemical Reactions Occur in the outer electron energy level Valance electrons
3Nuclear Reactions Occur in the nucleus of the atom Involve the NUCLEONSNucleons = protons & neutrons
4Strong Nuclear ForceProtons are positively charged and repel each other←+ +→Strong Nuclear Force = the force that causes the protons and neutrons in the nucleus to stick together and holds the nucleus tightly together.
5RadioactivityWhen the strong force of an atom is not strong enough to hold the nucleus together, then the atom tends to decayThe atoms are considered unstable, or radioactiveThe process of decay is called radioactivity and in the process particles and energy are released and the atom is changed into another type of atom
6ISOTOPESAtoms of the same element with a different number of neutrons.Ex: carbon-12 & carbon-14Carbon-126 protons6 neutrons6 electronsCarbon-148 neutronsCarbon 12 is a stable isotope of carbon. Carbon-14 is unstable or radioactive because the addition of the two neutrons have disrupted the strong force and made the nucleus start to decay, or break apart.
8ALPHA PARTICLE 2 protons & 2 neutrons nucleus of a helium atom weakest type of radiationcan be stopped by a piece of paper12 inches max. distance travel
9What happens to the numbers of particles in the nucleus after alpha decay?
10BETA PARTICLE an electron emitted from around the nucleus A neutron splits into a proton & electronThe electron is expelled out of the nucleusThe proton stays and increases the number of protons by one.The atomic number of the element increases by oneThe element changes into the next higher element on the periodic table.100x stronger than an alpha particle
11What happens to the numbers of particles in the nucleus after beta decay?
12Gamma Rays An electromagnetic wave A packet of energy The energy readjustment in the nucleusMost powerful form of radiationThe sun is a great source of gamma radiation
13Gamma Radiation, ContGamma rays are very harmful to cells. They can damage the DNA of your cells and mutate them, which can cause cancerHigh amounts of gamma ray exposure can cause deathLow amounts are normal and you are exposed to them all the timeCannot be easily blocked. Inches of concrete lined with lead can stop a gamma ray
16Antoine Henri Becquerel In 1896, radioactivity was first discovered.Used uranium salts = placed them near a photographic film plate.exposed the film (below)Awarded Nobel Prize in 1903 in Physics
17Pierre & Marie Curie (1898)Discover the radioactive properties of radium & poloniumTogether awarded the Nobel Prize in 1903 (physics) along with Henri BecquerelMarie is award a second Nobel Prize in 1911 (chemistry)Pierre is killed in an accident in 1906, Marie continues working with radioactive substances. She eventually dies of cancer
18Transmutation= changes from one element to another element during α and β decay.Alpha Decay = mass number decreases by 4 and the atomic number decreases by 2Beta Decay = mass number does not change and the atomic number increases by 1
19Alpha Decay Uranium-238 has 92 protons After alpha decay (2 protons & 2 neutrons leave the nucleus)Becomes Thorium-234 and has 90 protons
20Beta Decay Carbon-14 has 6 protons & 8 neutrons After beta decay (a neutron is split into a proton and electron & the electron is expelled from the nucleus)Becomes Nitrogen-14 and has 7 protons and 7 neutrons
21Half Life= the time it takes for one half of the mass of a radioactive substance to decay.Ex: carbon-14 = 5730 years100 gram sampleIn 5730 yrs = 50 grams C-14 & 50 grams N-14In11,460 yrs = 25 grams C-14 & 75 grams N-14In 17,190 yrs = 12.5 grams C-14 & 87.5 grams N-14
22Radioactive DatingHalf life is used by scientists to find out how old a fossil or a rock isCarbon 14 is often used to date fossilsWhat type of isotope used depends on the material being datedUranium is often used to date rocks because many rocks contain uranium already
23Detecting Radioactivity Cloud chambers track alpha and beta particlesChamber is filled with a cloud of vaporAlpha particles leave short thick trailsBeta particles leave long thin trails
24Bubble ChamberHolds a super heated liquid that doesn’t boil due to high pressureWhen a radioactive particle passes through the liquid, trails of bubbles form
25Geiger Counter Pops or clicks in the presence of radiation Uses electricity and current to cause a flow of electronsThe current is amplified to produce a clicking sound
26Background Radiation You are exposed to radiation every day Sources of background radiation vary and amounts are usually not harmful
28Nuclear Fission the splitting of the nucleus into two smaller nuclei Neutrons are used to split the nucleusAdditional neutrons are released to continue on to hit/split other nuclei
29Chain ReactionsCritical Mass (required) = concentration of radioactive atoms in a sample.Controlled Chain Reaction = many of the neutrons that are produced are absorbed in “control rods” prevent excess energy to be released.Ex. Nuclear Power PlantsUncontrolled Chain Reaction = all the neutrons are allowed to continue to hit/split other nuclei causing massive amounts of energy to be released all at once.Ex. Atomic Bomb (used on Japan in 1945)
31Generating Electricity Nuclear power is only one way to generate electricityIt is often cheaper and easier than other forms of energy (ie using wind or coal or water)However, there are safety concerns that you must take into consideration
32Nuclear Reactors Used to generate electricity Used to power ships, submarinesRisk of meltdown, must be kept cool to prevent uncontrolled chain reactions
34Three Mile Island Accident March 28, 1979– Harrisburg PA– Three Mile Island Nuclear Power Plant: A partial meltdown occurred in one reactor due to a stuck valve. Negligible amounts of radiation were released into the environment
35Chernobyl - April 26,1986 Power Plant in the Ukraine Explosion and fire that was caused by a power surge31 people died of acute radiation sicknessYou still can’t live in that area todayCrops were affected, many cases of cancer recorded, especially in children
37Fukushima - March 11, 2011Ongoing nuclear accident in Japan at the Fukushima power plantCaused partial or full meltdown to reactor, thanks to earthquake and TsunamiPower failure to coolant main causeEffects of the disaster are ongoing and unknown at this time
39Nuclear Fusion= the joining of two smaller nuclei into a single larger nucleusPowers the sun, very hard to duplicate on Earth because of the high pressure and temperature neededExtremely more powerful release of energy than fissionAlso known as a thermonuclear reactionex: H-bomb and the sun/stars