Examining the Link between the Nucleus & Radioactivity in Subatomic Particles

8/22/2019 Examining the Link between the Nucleus & Radioactivity in Subatomic Particles

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The Structure of Atoms


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Bonds Atoms want a full valence shell.

They can share or take electrons from anotheratom to fill.

They will do whatever is easiest - gain a

few to fill it

Orlose a few to drop down to their

already filled shell.

Carbon wants 4 electrons

so will form 4 bonds

both atoms gain electrons by

sharing to = full valence shell


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What about the Nucleus?

Positive Charge

Mass = 1

Elements are defined by thenumber ofprotons in the

nucleus

Protons:

Neutrons:

No Charge (are neutral)Mass = 1

Elements can have atoms with differing # of neutrons.

Atoms of the same element but w/ different # of neutrons

= I s o t o p e s


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Elementary particles What are Protons and Neutrons made up of?

Quarks!

What are Quarks made of?

They appear to be the fundamental particle --They are not made up of anything else.


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Quarks carry partial charges

Quark Chargeup + 2/3

down - 1/3

top + 2/3

bottom -1/3

charm +2/3

strange -1/3

Electrons have -1 Photons have 0 charge

Other elementary

particles you know:


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Add it up:

Neutron:

1 up quark +

2 down quarks

1x(+2/3)

2x(-1/3)

2x(+2/3)1x(-1/3)

+3/3

Proton:

2 up quarks +1 down quark

0/3


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What holds it all together?

Strong Force uses Gluons to hold quarks

together into protons and neutrons.

Nucleus held together by the Strong Forcetoo.

Very very strong, but acts only across very

very smalldistances such as the width of a

nucleus.


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Forces Interact via

force carrier particles Remember the basketball example.

Electromagneticforces carrier particle =

It interacts with chargedparticles

Strong forces carrier particle =

Gravitys force carrier particle =

Photon

Electrons & Protons

Gluon

Graviton


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Quick Quiz:

Which of the following are fundamental particles?

Electrons

Protons Neutrons

Quarks

Photons

Nuclei Atoms


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Standard Model of MatterComposed of atoms which are constructed of:

Quarks combined into protons & neutrons.

Quarks held together by strong force/gluons. Protons & Neutrons all held together to make a

Nucleus by strong force/gluons.

Electrons(a type of lepton a fundamental particle)


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CERN

Large Particle Collider


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Some nuclei are unstable

Strong force not quite strong enough in

large molecules.

These nuclei spontaneously spit outparticles from the nucleus.

Radioactivity!


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Types of Radioactivity

Alpha decay

Beta decay


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Alpha decay

Releases an alpha particle

2 protons & 2 neutrons

Whats in the nucleus now?


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Beta decay

A neutron kicks out a tiny,

negatively charged particle.

Whats in the nucleus now?

a beta particle


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Rate of Decay Half-life

For a SAMPLE of atoms, rate is constant.

Measure rate in half-life

Time it takes for half the sample to decay.

When a given atom decays is unpredictable .

So decay rate is the probability of decay over time.

What is wrong with this definition?

Half-life equals half the time it takes for the sample to decay


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Application: Radiometric Dating

See in-class worksheet

Examining the Link between the Nucleus & Radioactivity in Subatomic Particles

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