7.2 & 7.3 Nuclear Chemistry

Radioactivity, Isotopes, Half-Life, Fission and Fusion.

IsotopesIsotopes are atoms of the same element

(same number of protons) that have different number of neutrons = different atomic mass, same atomic number.

Changing one element to another or one isotope to another is called Transmutation

RadiationRadioactivity (aka

Radioactive decay) is decomposition of a nucleus to form a different nucleus.

It is the release of high-energy particles and rays of energy which change the nucleus.

Radioactivity occurs because of isotopes wanting to become stable.

7.2 Half LifeThe time it takes for exactly one-half of a

radio active sample to decay.The shorter the half life the faster the

decay.The half-life for a given isotope is always

the same.Using the half-life scientists can calculate

how much of a sample will be gone in a given amount of time.

Half life continued.For example Strontium-90

starts with 10 g, after it’s first half-life (29 years) it becomes 5 g, second half-life (58 years) is 25 g, and so on.

A decay curve is a curved line on a graph that shows the rate at which the sample it is decaying. (x= number of half lives, y axis = how much remaining)

Isotope PairsSince, we know that when isotopes wish

to become stable the change the particles in the nucleus through decay.

The sample before can change into a new element or isotope

The parent isotope is the one that decays and the daughter isotope is on of the products of the decay.

VideoThe Origins Of SpidermanBit by radioactive spider effected by

radioactive decay in a chemistry lab.

Quiz1. What measurement can compare the rate of radioactive decay?

a) Radiometric datingb) Radioactive microscopec) Decay curve

2. How many grams will be left over of a 100 g sample after 5 half lives?

a) 10.5b) 3.125c) 20

7.3 Nuclear ReactionsA nuclear reaction is when an atom

changes by gaining or releasing particles or energy. (Can release subatomic particles and gamma rays)

This happens because of nucleus wanting stability by removing particles.

Bombarding a nucleus with alpha & beta particles, or gamma rays causes a reaction.

Scientists can cause a reaction by making nuclei unstable, causing it make a reaction.

Nuclear FissionNuclear fission is the splitting of a heavy

nucleus into two lighter nuclei.Heavy nuclei tend to unstable because of

repulsive forces between their many protons.

The reactions releases a lot of energy along with the smaller nuclei and subatomic particles, from the binding force in the nucleus.

Fission is a large source for nuclear power from it’s energy.

Fission ContinuedSome nuclei while undergoing fission

can release subatomic particles, that can trigger more fission reactions this is called a chain reaction.

The number of fissions and the amount of energy released adds up quickly that can lead to violent explosions.

Fission is used for nuclear weapons, and nuclear power generators because of all the energy.

Since it difficult to control, power plants monitor and adjust constantly.

However, it produces radioactive waste that takes a long time to decay.

Nuclear FusionNuclear fusion is when a small nucleus combines to

produce a larger nucleus.Other subatomic particles and energy is released. Fusion occurs in the sun and other stars where

pressure and high temperature causes isotopes of hydrogen to collide creating enormous amounts of energy.

There is no technology capable of using the energy from fusion reactions. Because it is so strong from high pressure and temperature, it is impossible to control.

It could be used in nuclear weapons as it is seen as strong.

Nuclear EquationsA nuclear equation is a set of symbols that

indicates changes in the nuclei of atoms during nuclear reactions.

The sum of the mass numbers on each side of the equation stays the same.

The sum of the charges (atomic numbers) on each side of the equation stays the same.

Video• In this episode of spider man; A mad

scientist, Doctor Pretorius, escapes from prison and plots widespread devastation with a nuclear weapon he calls "The Kingdom Come Device."

Quiz1. Where does nuclear fusion occur?

a) In the sun and other starsb) Under groundc) Inside a power plant

2. A nuclear reaction can release a) Gamma Rays

b) Energyc) Subatomic Particles d) All of the above

3. A nuclear reaction is induced bya) alpha & beta particles , and gamma raysb) energyc) another atom

4. Nuclear fission releases a very large amount of….a) energyb) electronsc) neutrons