A nucleus can be specified By an atomic number and a

Mass number.

7

Nitrogen

N

AtomicNumber

(Z)

NameSymbol

14

MassNumber

(A)

The typical Nitrogen atom hasA mass number of 14.

It has 7 protons and 7 neutrons.

The atomic number never changes,However the mass can change.

All atoms are electrically Neutral, thus the number Of protons equals

the Number of electrons.

Symbol Name Explanation

A Mass Number The number of nucleons

Z Atomic Number The number of protons

N Neutron Number The number of neutrons

An isotope is when atoms of an Element having the same atomic

Number but different Neutron and mass number.

Hydrogen has 3 isotopes:HydrogenDeuterium

Tritium

Scientists measure Elements in AMU, or atomic

Mass units.

1 AMU = 1/12 (mass of Carbon)= 1.66 X 10-24 g

So, one proton or one Neutron are about

1 AMU each.

The strong nuclear force isAn attractive force that Overcomes the electrical

Repulsion between protons.

Nuclear reactions changeThe composition of An atoms nucleus!!

Binding energy is the energyReleased when nucleons bind

Together to form a Stable nucleus.

E = mc2

When a nucleus undergoes Nuclear decay, only three typesOf radiation can be released…

Alpha Beta

Gamma

NAME IDENTITY CHARGE PENETR-ATION

ALPHA

α

He-4

NUCLEI

2+ LOW

BETA

β

ELECTR-ONS

1- MEDIUM

GAMMA

γ

HIGH

ENERGY

X-RAY

NONE VERY

HIGH

Everybody thinks that this is so Hard, but there are only 2 rules…

The total of the atomic numbers on The left is that same as the total

On the right because chargeMust be conserved.

The total of the mass numbers on The left is the same as the total on

The right because mass must Be conserved.

131I 131Xe + 0β53 54 -1

This is the nuclear equationThat describes the beta Decay of iodine – 131.

The numbers ALWAYS balance!

One of the isotopes of radium, 226 Ra, decays by alpha

Emission. What is the resultingDaughter element?

88

226 Ra 222 Rn + 4 α88 86 2

As things decay, it can Be measured.

The SI unit of radioactivity isThe becquerel, Bq.

1 Bq = 1 decay per second

The half-life is the time requiredTo half the original nuclei

Of a radioactive material to Undergo radioactive decay.

T ½ = 0.693Decay constant

The 1/2 life of a radium nucleus is 5 X 1010s. A sample contains

3 X 10 16 nuclei. What is the decayConstant for this decay? How Many radium nuclei will decay

Per second?

Constant = 1.4 X 10-11

Activity = 420000 Bq

There are 2 types of nuclear Reactions, fission & fusion.

Stable nuclei can be made Unstable by bombarding them

With extra neutrons.

Heavy nuclei can undergoNuclear fission.

Nuclear fission is the breakingApart of a nucleus.

When nuclear fission occurs,Neutrons are released and can

Trigger a chain reaction.

Light nuclei can undergo Nuclear fusion.

Nuclear fusion is when two Nuclei are squished together.

Stars work like this, up until Iron - 58, (the most stable element).Fusing elements after this require

Energy, thus are made in A supernova.

All things in the universe are Created by very, very tiny

Pieces of matter.

Many new particles have been Produced in accelerators.

There are 4 fundamental Interactions in nature…

Strong, Weak,Electromagnetic & Gravitational

A force can be thought of as Mediated by an exchange

Of particles.

Leptons are thought to be Elementary particles.

Hadrons include mesons & baryons.

Hadrons are thought to be madeOf quarks.

There are 6 quarks…

Up, Down, Charm,Strange, Top, Bottom.

The standard model can help Explain the early universe.