Chemistry Chapter 7.7-7.9 - Radiation

What is Nuclear Chemistry?

The study of the atomic nucleus, its reactions, and radioactivity

What is a chemical reaction?

a change in compounds because of forming or breaking molecular bonds

What is a nuclear reaction?

a change in elemental identity because of radioactive decay, fission, or fusion

In chemical reactions, reactions form new...

substances based on the elements present in the reactants

In chemical reactions, energy changes are...

relatively small

In chemical reactions, energy comes from...

breaking and forming chemical bonds

In chemical reactions...

valence electrons drive the reaction

In nuclear reactions, reactions form new...

isotopes or elements

In nuclear reactions, energy changes are...

extremely large

In nuclear reactions, energy comes from...

the binding energy of the nucleus

In nuclear reactions...

a change in the nucleus drives the reaction

What competing forces exist within a nucleus?

Repulsive Coulombic forces (+p repel each other) and nuclear strong forces (holds it together)

What determines the stability of a nucleus?

The ratio of protons to neutrons

Above what number of protons are atoms all unstable?

84

What usually stabilizes a large atom?

The addition of neutrons

Above the band of stability...

isotopes have too many neutrons

Below the band of stability...

isotopes have too many protons

Isotopes above and to the right of the band of stability....

have too many protons and neutrons

Radioactive decay is...

spontaneous disintegration of an unstable nucleus often resulting in the formation of a new element

What determines the probability of when an atom will decay?

An atom's nuclear half life

What are nuclear half-lives?

A calculation of at what time half of a sample will have decayed

Which is possible: a prediction of a nucleus's decay time or a prediction of a sample's decay time?

A sample's decay time

Why does carbon dating with the isotope carbon-14 work?

Because living organisms have the same ratio of carbon-12 to carbon-14 as in the atmosphere, the older a sample is (up to 50,000 years) the less carbon-14 it will have (living organisms absorb carbon-14 by breathing)

Type the particle notation for carbon dating.

147N + 10n -\> 146C +11p

What is the attractive force that holds nuclei together?

The nuclear strong force

Nuclear fission is...

a nuclear reaction in which a neutron splits a large nucleus into two or more smaller nuclei releasing a large amount of energy and extra neutrons

Where does nuclear fission occur?

In nuclear power plants and atom bombs

Nuclear fusion is...

a nuclear reaction in which two or more smaller nuclei are combined to form one larger nucleus releasing more energy than fission

What is required for fusion?

Extremely high temperature and pressure

Where does fusion occur?

Fusion occurs in stars and hydrogen bombs

Nuclear fission and fusion both work when nuclei split or combine into....

new atoms with more binding energy

Why does fusion release more energy than fission?

Because fusion combines atom's nuclear strong force which is stronger than the energy released when an atom splits

Which atom has the highest binding energy?

Fe-56

Elements that are smaller than Fe-56 release energy through...

fusion

Elements that are larger than Fe-56 release energy through...

fission

Type the particle notation for a proton.

11p

Type the particle notation for a neutron.

10n

Type the particle notation for an alpha particle.

42He or 42a

Type the particle notation for a bata particle.

0-1e

Type the particle notation for a gamma particle.

00Y

Type the particle notation for a positron.

11e

What is alpha decay?

when an atom loses an alpha particle because it has more than 83 protons

What material can stop the penetration of alpha decay?

Paper, skin, or clothes

What is beta decay?

when a atom with too many neutrons loses an electron by converting a neutron into a proton, releasing an electron

What material can stop the penetration of beta decay?

aluminum foil

What is gamma radiation (decay)?

when an atom has excess energy and releases a gamma wave

What material can stop the penetration of gamma radiation?

Several inches of lead or feet of concrete

What is neutron emmission?

When an atom that is too heavy and above the band of stability sheds a neutron

What material can stop the penetration of a neutron?

Hydrogen-rich material (eg. water)

What is electron capture?

When an atom that is too light and below the band of stability captures an electron to convert a proton into a neutron and releases gamma radiation

What is positron emmission?

When an atom that is too light and below the band of stability emits a positron (opposite of beta decay)

What is a decay series?

a series in which a radioactive nucleus will decay repeatedly into a stable element