chapter 25 - acadia.k12.la.us · title: powerpoint presentation author: debbie munson created date:...

25.1 Nuclear Radiation >

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Chapter 25Nuclear Chemistry

25.1 Nuclear Radiation

25.2 Nuclear Transformations

25.3 Fission and Fusion

25.4 Radiation in Your Life



What makes some types of radiation

more dangerous than other types?

CHEMISTRY & YOU

Lengthy or

frequent exposure

to X-rays can

damage cells in

your body.



Radioactivity

Radioactivity

How do nuclear reactions differ from

chemical reactions?



Radioactivity

In 1896, the French chemist Antoine

Becquerel made an accidental discovery.

• He was studying the ability of uranium salts

that had been exposed to sunlight to fog

photographic film plates.



Radioactivity

In 1896, the French chemist Antoine

Becquerel made an accidental discovery.

• He was studying the ability of uranium salts

that had been exposed to sunlight to fog

photographic film plates.

• During bad weather, when Becquerel could not

expose a sample to sunlight, he left the

sample on top of the photographic plate.

• When he developed the plate, he discovered

that the uranium salt still fogged the film.



Radioactivity

Two of Becquerel’s associates were Marie

and Pierre Curie.

• The Curies were able to

show that rays emitted by

uranium atoms caused the

film to fog.

• Marie Curie and her

husband Pierre shared the

1903 Nobel Prize in physics with Becquerel for

their pioneering work on radioactivity.



Radioactivity

Marie Curie used the term radioactivity to

refer to the spontaneous emission of rays

or particles from certain elements, such as

uranium.



Radioactivity

Marie Curie used the term radioactivity to

refer to the spontaneous emission of rays

or particles from certain elements, such as

uranium.

• The rays and particles emitted from a

radioactive source are called nuclear

radiation.



Radioactivity

Radioactivity, which is also called

radioactive decay, is an example of a

nuclear reaction.

• Nuclear reactions begin with unstable

isotopes, or radioisotopes.



Radioactivity



nuclear reaction.



• Atoms of these isotopes become more stable

when changes occur in their nuclei.



Radioactivity



nuclear reaction.



• Atoms of these isotopes become more stable

when changes occur in their nuclei.

• The changes are always accompanied by the

emission of large amounts of energy.



Radioactivity

Unlike chemical reactions, nuclear

reactions are not affected by

changes in temperature, pressure, or

the presence of catalysts. Also,

nuclear reactions of a given

radioisotope cannot be slowed

down, sped up, or stopped.



Radioactivity

Radioactive decay is a spontaneous

process that does not require an input of

energy.



Radioactivity



energy.

• If the product of a nuclear reaction is

unstable, it will decay too.



Radioactivity



energy.



• The process continues until unstable isotopes

of one element are changed, or transformed,

into stable isotopes of a different element.



Radioactivity



energy.



• The process continues until unstable isotopes

of one element are changed, or transformed,

into stable isotopes of a different element.

• These stable isotopes are not radioactive.



Why do unstable isotopes undergo

nuclear reactions?



Why do unstable isotopes undergo

nuclear reactions?

Unstable isotopes undergo nuclear reactions

so that they may be changed, or

transformed, into stable isotopes.



Types of Radiation

Types of Radiation

What are three types of nuclear

radiation?



Types of Radiation

Radiation is emitted during radioactive

decay.

Three types of nuclear radiation are

alpha radiation, beta radiation, and

gamma radiation.



Characteristics of Some Types of Radiation

Type Consists of Symbol ChargeMass

(amu)

Common

source

Penetrating

power

Alpha

radiation

Alpha particles

(helium nuclei)a, 2+ 4

Radium-

226

Low

(0.05 mm

body tissue)

Beta

radiation

Beta particles

(electrons)b, 1– 1/1837

Carbon-

14

Moderate

(4 mm body

tissue)

Gamma

radiation

High-energy

electromagnetic

radiation

g 0 0 Cobalt-60

Very high

(penetrates

body easily)

He4

2

e0

–1

Interpret Data



Types of Radiation

Alpha Radiation

Some radioactive sources emit

helium nuclei, which are also called

alpha particles.



Types of Radiation

Alpha Radiation



alpha particles.

• Each alpha particle contains two

protons and two neutrons and has a

double positive charge.



Types of Radiation

Alpha Radiation



alpha particles.

• Each alpha particle contains two

protons and two neutrons and has a

double positive charge.

• An alpha particle is written He or a.42

– The electric charge is usually omitted.



Types of Radiation

Alpha Radiation

The radioisotope uranium-238 emits alpha

radiation and is transformed into another

radioisotope, thorium-234.

U238

92

Uranium-238

Th +234

90

Thorium-234

He (a emission)4

2

Alpha particle

Radioactive

decay



Types of Radiation

Alpha Radiation

When an atom loses an alpha particle, the

atomic number of the product is lowered

by two and its mass number is lowered by

four.

• In a balanced nuclear equation, the sum

of the mass numbers (superscripts) on

the right must equal the sum on the left.

• The same is true for the atomic numbers

(subscripts).

U238

92 Th +234

90 He4

2→



Types of Radiation

Alpha Radiation

Because of their large mass and charge,

alpha particles do not travel very far and

are not very penetrating.

• A sheet of paper or the surface of your skin

can stop them.

• But radioisotopes that emit alpha particles

can cause harm when ingested.

– Once inside the body, the particles don’t have to

travel far to penetrate soft tissue.



Types of Radiation

Beta Radiation

An electron resulting from the breaking apart

of a neutron in an atom is called a beta

particle.

• The neutron breaks apart into a proton, which

remains in the nucleus, and a fast-moving

electron, which is released.

n1

0

Neutron

p +1

1

Proton

e 0

–1

Electron

(beta particle)

→



Types of Radiation

Beta Radiation

The symbol for the electron has a subscript

of –1 and a superscript of 0.

• The –1 represents the charge on the electron.

• The 0 represents the extremely small mass of

the electron compared to the mass of a proton.

n1

0

Neutron

p +1

1

Proton

e 0

–1

Electron

(beta particle)

→



Types of Radiation

Beta Radiation

Carbon-14 emits a beta particle as it decays and

forms nitrogen-14.

• The nitrogen-14 atom has the

same mass number as

carbon-14, but its atomic

number has increased by 1.

• It contains an additional

proton and one fewer neutron.

C14

6

Carbon-14

(radioactive)

N +14

7

Nitrogen-14

(stable)

e (b emission)0

–1

Beta particle

→



Types of Radiation

Beta Radiation

A beta particle has less charge than an

alpha particle and much less mass than an

alpha particle.

• Thus, beta particles are more penetrating than

alpha particles.

– Beta particles can pass through paper but are

stopped by aluminum foil or thin pieces of

wood.



Types of Radiation

Beta RadiationBecause of their opposite charges, alpha and beta

radiation can be separated by an electric field.

• Alpha particles move toward the negative plate.

• Beta particles move toward the positive plate.

• Gamma rays are not deflected.



Types of Radiation

Gamma Radiation

A high-energy photon emitted by a radioisotope is

called a gamma ray.

• The high-energy photons are a form of

electromagnetic radiation.

• Nuclei often emit gamma rays along with alpha or beta

particles during radioactive decay.

Ra +226

88

Radium-226

Th230

90

Thorium-230

He + g4

2

Alpha

particle

Gamma

ray

→

Pa +234

91

Protactinium

-234

Th234

90

Thorium-234

e + g0

–1

Beta

particle

Gamma

ray

→



Types of Radiation

Gamma rays have no mass and no

electrical charge.

• Emission of gamma radiation does not alter

the atomic number or mass number of an

atom.

Gamma Radiation



Types of Radiation

Because gamma rays are extremely penetrating,

they can be very dangerous.

• Gamma rays pass easily through paper, wood, and the

human body.

• They can be stopped, although not completely, by several

meters of concrete or several centimeters of lead.

Gamma Radiation



Gamma rays can be dangerous because

of their penetrating power. What property

determines the relative penetrating power

of electromagnetic radiation?

CHEMISTRY & YOU



Gamma rays can be dangerous because

of their penetrating power. What property

determines the relative penetrating power

of electromagnetic radiation?

CHEMISTRY & YOU

The wavelength and energy of

electromagnetic radiation determine its

relative penetrating power. Gamma rays

have a shorter wavelength and higher

energy than X-rays or visible light.



Which process involves a radioactive

nucleus releasing a high-speed

electron?

A. oxidation

B. alpha emission

C. beta emission

D. gamma radiation



A. oxidation

B. alpha emission

C. beta emission

D. gamma radiation

Which process involves a radioactive

nucleus releasing a high-speed

electron?



Key Concepts

Unlike chemical reactions, nuclear

reactions are not affected by changes in

temperature, pressure, or the presence of

catalysts. Also, nuclear reactions of a

given radioisotope cannot be slowed

down, sped up, or stopped.

Three types of nuclear radiation are alpha

radiation, beta radiation, and gamma

radiation.



Glossary Terms

• radioactivity: the process by which nuclei

emit particles and rays

• nuclear radiation: the penetrating rays and

particles emitted by a radioactive source

• radioisotope: an isotope that has an unstable

nucleus and undergoes radioactive decay



Glossary Terms

• alpha particle: a positively charged particle

emitted from certain radioactive nuclei; it

consists of two protons and two neutrons and

is identical to the nucleus of a helium atom

• beta particle: an electron resulting from the

breaking apart of neutrons in an atom

• gamma ray: a high-energy photon emitted by

a radioisotope



Electrons and the Structure of Atoms

• Unstable atomic nuclei decay by emitting

alpha or beta particles.

• Often gamma rays are emitted too.

BIG IDEA



END OF 25.1

chapter 25 - acadia.k12.la.us · title: powerpoint presentation author: debbie munson created date:...

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