Unit 4. In this part of the unit, we will focus on the nucleus! It’s very small (10 -13 cm) ...

Nuclear ChemistryUnit 4

Parts of an atom

Radiation

In this part of the unit, we will focus on the nucleus! It’s very small (10-13 cm)

It’s very dense (1.6 ×1014 g/cm3)

A lot of energy holds it together!(millions of times more than involved in chemical

reactions!)

Many nuclei are RADIOACTIVE!

They spontaneously decompose or DECAY (break apart) forming a different nucleus & producing

one or more particles

3 Main Types of Decay Particles

Alpha (α) particles Slow moving

nucleus of a helium atom.

Not very dangerous, can be stopped by▪ Skin▪ A piece of paper

3 Main Types of Decay Particles

Beta ( β) Particles Faster moving

electrons Are harmful Can be stopped by

wood or metal sheets

3 Main Types of Decay Particles Gamma (γ)

Particles High-energy

photon of light Very dangerous Partially stopped by

6 inches of lead or 6 feet of concrete

Fission

Process of splitting a heavy nucleus into two more stable nuclei with smaller mass numbers

Releases a lot of energy

Fission

Chain reaction When you have a

lot of a radioactive substance and the fission of one nucleus gives off particles that hit other nuclei that give off more particles that hit more nuclei. . .

Fission

Critical Mass The mass of

material required to produce a chain reaction.

Fission: Where is it used?

Fission: Where is it used?

NUCLEAR BOMBSNUCLEAR BOMB EXPLOSION http://www.youtube.com

/watch?v=zsTRxXvQY0s

How fission bombs are made

http://www.youtube.com/watch?v=fIbACkLU-38

Time-lapse video of all bombs exploding

http://www.youtube.com/watch?v=_W_lLhBt8Vg

Fission: Where is it used?NUCLEAR SUBMARINES

Fission: Where is it used?NUCLEAR IMAGING IN MEDICINE

Uses computers, detectors, & radioactive substances to look inside the human body PET Scan – positron

emission tomography SPECT scan – single

photon emission computed tomography

Cardiovascular imaging Bone scans

TO DETECT

Tumors Aneurysms (weak

spots in blood vessel walls)

Irregular or inadequate blood flow to various tissues

Blood cell disorders & inadequate functioning of organs, such as the thyroid

Fission: Where is it used?

PET SCAN MACHINE PET SCAN

Fusion

Process of combining two light nuclei to form a heavier, more stable nucleus.

Produces a lot more energy than fission!

Is self-sustaining (chain –reaction) at more than 40,000,000°

Fusion: Where is it used?

Note: There are no PURE fusion bombs because of the extremely high temperatures needed to sustain a fusion chain reaction.

Fusion: Where is it used?

Stars are powered by nuclear fusion in their cores.

Small stars: The smallest stars only convert hydrogen into helium.

Medium-sized stars (like our Sun): Late in their lives, when the hydrogen becomes depleted, stars like our Sun can convert helium into oxygen and carbon.

Massive stars (greater than five times the mass of the Sun): When their hydrogen becomes depleted, high mass stars convert helium atoms into carbon and oxygen, followed by the fusion of carbon and oxygen into neon, sodium, magnesium, sulfur and silicon. Later reactions transform these elements into calcium, iron, nickel, chromium, copper and others. When these old, large stars with depleted cores supernova, they create heavy elements (all the natural elements heavier than iron) and spew them into space, forming the basis for life.

Fusion: Where is it used?

Creating the elements- in stars

https://www.youtube.com/watch?v=neMEo8ZrwuI