No Warmup TodayNo Warmup TodayTODAY we will review TODAY we will review Atoms/Ions and learn Atoms/Ions and learn about radioactivityabout radioactivity

Test on Friday will be Test on Friday will be about atoms, periodic about atoms, periodic table, ions, isotopes and table, ions, isotopes and electrons (valence and electrons (valence and shells) and radioactivityshells) and radioactivity

RadiationRadiation

What holds the nucleus What holds the nucleus together? together?

Protons are pushing apart.Protons are pushing apart.

Neutrons hold it Neutrons hold it together via nuclear together via nuclear

force, or force, or ““strongstrong”” force. force.

If nuclear force is If nuclear force is greater than repulsion, greater than repulsion, nucleus stays together.nucleus stays together.

But what if the forces But what if the forces arenaren’’t strong enough to t strong enough to

hold everything in hold everything in place? place?

Radiation Radiation click to watch :click to watch :

http://ed.ted.com/lessons/radioactivity-expect-the-unexpected-steve-weatherall

Who? The 3 Who? The 3 types of types of

Radioactive Radioactive Decay:Decay:

•Alpha: Particle made of two Alpha: Particle made of two protons, two neutrons. protons, two neutrons.

•““HeavyHeavy”” particle particle

•Positive charge Positive charge

•Can be stopped by a sheet Can be stopped by a sheet of paperof paper

•Change Identity of parent Change Identity of parent when lost, loses 2 protons when lost, loses 2 protons and 2 neutrons and 2 neutrons atomic # -2 atomic # -2 atomic mass -4atomic mass -4

4He+

2

Who? The 3 Who? The 3 types of types of

Radioactive Radioactive Decay:Decay:

•Beta: an electron from Beta: an electron from nucleus – a neutron nucleus – a neutron breaks apart breaks apart

•Have a negative charge Have a negative charge and weigh less than a and weigh less than a neutron or proton. neutron or proton.

•Will travel several Will travel several meters in air, meters in air, stopped stopped by flesh or plastic. by flesh or plastic.

•Changes identity of Changes identity of atom –neutron turns atom –neutron turns into a proton:into a proton: atomic # +1 atomic # +1

0e-1

Three types of Three types of Radioactive Radioactive

Decay:Decay:

•Gamma: An Gamma: An electromagnetic wave, electromagnetic wave, NOT a particleNOT a particle

•Short wavelengths and Short wavelengths and high frequency – HIGH high frequency – HIGH ENERGYENERGY

•DANGEROUS. Can do DANGEROUS. Can do serious damage to living serious damage to living tissue due to their tissue due to their energyenergy

•Come from the excited Come from the excited nucleus AFTER it gives nucleus AFTER it gives off alpha or beta particleoff alpha or beta particle

•Can go through 2-3 cm Can go through 2-3 cm of leadof lead

Why Why ““decay?decay?””When an atom gives off alpha or beta When an atom gives off alpha or beta particles, it transforms into other particles, it transforms into other elementselements. Another word for this . Another word for this transformation is transformation is decaydecay..

For example, UraniumFor example, Uranium238238 will lose an will lose an alpha particle and turn into Thoriumalpha particle and turn into Thorium234234 or: or:

238238UU9292 -> -> 234234ThTh9090 + + 44HeHe2+2+

Uranium loses two protons and its atomic Uranium loses two protons and its atomic number AND mass number changes. number AND mass number changes. Thorium-234 keeps decaying…13 more Thorium-234 keeps decaying…13 more reactions to become stable at Pb-206. reactions to become stable at Pb-206. …..it eventually turns into lead…..it eventually turns into lead

Two Types of Two Types of Nuclear Nuclear

Reactions:Reactions:Fission – Fission – one large one large atom splits when a atom splits when a neutron hits a neutron hits a nucleus and splits nucleus and splits it apart, releasing it apart, releasing energyenergy

THINK DIVISIONTHINK DIVISION

Found in two Found in two places:places:

UNCONTROLLED FISSION

http://www.youtube.com/watch?v=11e8XyUBqRQ

Nuclear Energy, made simple

CONTROLLED FISSION

Two Types of Two Types of Nuclear Nuclear

Reactions:Reactions:FusionFusion – Two – Two smallsmall nuclei fuse nuclei fuse togethertogether

THINK FUSE TOGETHERTHINK FUSE TOGETHER

While weWhile we’’re re talking radiation…talking radiation…

Half-lifeHalf-life: : The period of time for a substance The period of time for a substance undergoing decay to decrease by halfundergoing decay to decrease by half. .

For example, Uranium-238For example, Uranium-238’’s half-life is 4.46 s half-life is 4.46 billion years. Slow decay by emitting an billion years. Slow decay by emitting an alpha particle. If I had 1,000 g of U-238, in alpha particle. If I had 1,000 g of U-238, in 4.46 billion years, I would have 500g of U-4.46 billion years, I would have 500g of U-238. 238.

Carbon-14Carbon-14’’s half-life is 5730 years. Useful s half-life is 5730 years. Useful for dating organic items of age since itfor dating organic items of age since it’’s in s in all living tissue. all living tissue.

In other words…In other words…

Parent Element: The original one that is going through radioactive decay -unstable

Daughter Element: Daughter Element: The element that the The element that the parent changed into parent changed into (replaces the parent) (replaces the parent) more stablemore stable

LetLet’’s try it…s try it…say, a half life of 30 years say, a half life of 30 years

and and 500 g. How 500 g. How much left in 90 years? much left in 90 years?

Half life = 30 years, how many half lives in 90?90/3 = 3

1st Half Life- after 30 years, we would have: 250 g

2nd half life-after 60 years would be ½ of 250g: 125g

3rd half life- after 90 years would be ½ of 125: 62.5g

Fukushima, over a year ago

Nuclear Power

Benefits? Are there greenhouse gasses?

Is it efficient?

Is there waste?

Risks? Coal vs. Natural Gas vs. Oil vs. Nuclear