Nuclear chemistry Chapter 12

I lied to you Until now we have said that an element cant be broken down into anything else. This was a lie (sorry). In some cases elements can actually be changed into other elements.

Transmutation When one element turns into a different element it is called transmutation. There are two ways this can happen. Natural and Artificial.

Natural transmutation When an element does not have a stable proton to neutron ratio in the nucleus and protons, neutrons or electrons are shot out of the atom More on this later

Artificial transmutation Artificial transmutation is when a neutron is shot at a atom, and it forces the nucleus to ‘break apart’. This usually causes more protons and neutrons to shoot out into other atoms and a chain reaction occurs.

The difference A natural transmutation doesn’t need neutrons ‘shot at it’ to occur. An artificial transmutation does need neutrons ‘shot at it’ to occur.

More on radiation. When an element is unstable and it ‘shoots out particles’ there are 4 main particles that get ‘shot out of the nucleus’ 1.Alpha 2.Beta 3.Positron 4.Gamma

Alpha Decay Alpha decay is when a nucleus shoots out a particle of 2 protons and 2 neutrons This is symbolized as This is symbolized as Since it has 2 protons it is a helium atom it is a helium atom

Alpha Decay When an atom undergoes alpha decay it loses 2 protons and 2 neutrons, and becomes a different element.

Alpha Decay

Beta decay A beta particle is another way of saying an electron. During Beta decay a nucleus ‘shoots out’ an electron--- and has a neutron turn into a proton

Beta Decay When something undergoes beta decay it actually ‘gains a proton’

Positron Decay Positron decay is when a nucleus ‘shoots out’ a proton and goes down by 1 atomic number.

Gamma Decay Gamma rays are when an atoms gives off only energy and no mass It is the highest energy It is the highest energy and it has the highest and it has the highest penetrating power making penetrating power making it the most dangerous it the most dangerous

Table O Table O on your reference table has all the decay symbols.

Table N Different radio active elements ‘shoot off’ different particles. If you look at table N on your reference table it has all the types of decays listed.

Balancing transmutations Balancing transmutations is exactly like doing algebra...Balance these..

Decay All radioactive atoms have different speeds of decay. Something's decay within seconds. Others take thousand of years.

Decay When we have a sample of a radio active element it is impossible to know which atom will decay next… But we can determine the amount of time it takes for half of the atoms to decay.

Half Life The amount of time it takes for half of a sample to decay is called its half life.

Uses of radio active material Carbon dating. All living material uses lots of carbon, and there is a tiny amount of radio active carbon (C-14) mixed with other carbons

Carbon dating When people die they stop taking in carbon, and the radio active carbon decays. If the average person has 15 grams of radio active carbon, and a mummy has 7.5 grams of radioactive carbon it has gone thru one half life ( 5730 years old).

If a spear found in a cave has 1/8 the amount of radio active carbon that normal wood has it went thru _______half lives… Meaning it is ________years old.

Medical applications Radio active iodine (I-131) is used to treat types of thyroid cancers. Radio active Cobalt-60 – is used to kill cancer cells also. Cesium-167 is used to kill bacteria in food (irradiate)

Risks Radio active substances can be used for lots of energy, but they have big risks if a disaster happens. Radioactive materials can also leak out.