Nuclear Energy

Nuclear Reactions

HS-PS1-8, HS-ESS1-1, HS-ESS1-3

Number of Protons in an Atom

●

The number of protons in an atom is equal to the atomic number of
that element.

●

Looking at the periodic table to the right,
how many protons is in:
○

chlorine (Cl)

○

argon (Ar)

○

tin (Sn)

○

sulfur (S)

○

fluorine (F)

Isotopes

●

Neutrons weigh about the same as protons
and help make up most of the atom’s mass.

●

Changing the amount of protons in an atom
changes the element.

●

Changing the amount of electrons in an
atom makes it an ion.

●

Changing the amount of neutrons in an atom
makes it an isotope of that element.

●

The atomic mass at the bottom is an
AVERAGE of all the different isotopes and
their percentages.

Isotope Symbols

●

Normally atoms are represented by only their symbol.

●

In the example 54 is the atomic mass and 26 is the atomic
number.

●

To find the number of neutrons subtract the two.
○

Example: 54 - 26 = 28 neutrons.

●

If the atom is an ion then a + or - and a number gets put on
the upper right of the element symbol.

●

If the atom is an isotope the atomic mass of that isotope is
put into the upper left corner and the atomic number in the
bottom left corner.

Writing Isotopes

●

Isotopes can also be written as the mass number then the name of
the element.
○

Example: Carbon-13

●

To find out the number of neutrons subtract the atomic number from
the atomic mass.
○

Example: Carbon-13 which has the atomic number of 6 so
carbon-13 has 7 neutrons.
■

Neutral carbon has 6 neutrons.

Isotope Practice

a.

Helium-3

b.

Hydrogen-1

c.

Carbon-12

g.

D

h.

D

i.D

j.D

d.

Carbon-14

e.

Uranium-235

f.Uranium-239

k.

D

l.

D

m.

D

n.

D

Write the following as either isotopic notation (a-f) or hyphen notation
(g-n).

Nuclear Reactions

●

Remember the nucleus of the atom is composed of protons and
neutrons.

●

And in all the interactions that have been discussed only the
interactions between electrons of 2 or more atoms have been
brought up.

●

BUT what if the nucleus of the atom is changed? Can the nucleus
even be changed? And what happens IF we can change the
nucleus?

●

Enter nuclear reactions!

Nuclear Reactions and Energy

●

Molecules are constantly being broken and reformed into different
molecules. Breaking and forming bonds both require energy.
○

Considering breaking and forming bonds between molecules
happen constantly do you think a lot of energy is required to
perform these reactions?

●

Nuclear reactions can happen spontaneously but typically have large
amounts of energy associated the breaking or transition of protons
and neutrons in the nucleus.
○

Do you think the energy associated with the atomic bomb could
be accomplished with a chemical reaction?

Fission

●

When an atom splits into 2 or more parts.
○

Also called radioactive decay

●

Fission can be spontaneous or can be purposely caused (think
nuclear power and nuclear weapons)

●

Radioactive decay happens to ALL elements, some more rapidly
than others.
○

The more stable an element or isotope is, the longer it takes to
decay. It is like the difference between a cheap piece of furniture
and a sturdy well-built one.

○

How fast the element decays is called half-life.

○

Each element and any isotopes for that element have different
half-lives.

Fission

Radioactive Decay - Alpha

●Elements that undergo alpha decay emit an alpha particles that
contains 2 protons and 2 neutrons.

○
Alpha particles are the equivalent of a helium nucleus.

Radioactive Decay - Alpha Practice

9.

S

10.

S

11.

S

12.

S

13.

S

14.

s

●

Determine the elemental isotope that is the result of alpha decay of
the following isotopes. Write your answer in hyphen notation.

1.

Carbon-13

2.

Actinium-228

3.

Bismuth-207

4.

Gold-170

5.

Argon-41

6.

Cerium-144

7.

Chlorine-32

8.

Copper-60

Radioactive Decay - Beta Minus

●

Beta minus decay occurs when a neutron is transformed into a
proton and emits an electron.
○

This changes the atomic number of the isotope by +1 and
change the number of neutrons by -1.
■

Example: Beta decay of argon-40 will result in potassium-40
with the number of neutrons in potassium as 21.

Beta Minus Decay Practice

●

Determine the elemental isotope and # of neutrons that is the result
of beta minus decay that emits an electron of the following isotopes.

1.

Carbon-13

2.

Actinium-228

3.

Bismuth-207

4.

Gold-170

5.

Argon-41

6.

Cerium-144

7.

Chlorine-32

8.

Copper-60

9.

S

10.

S

11.

S

12.

S

13.

S

14.

s

Radioactive Decay - Beta Plus

●

Beta plus decay occurs when a proton is transformed into a neutron
and emits a positron (positive electron).
○

This changes the atomic number of the isotope by -1 and the
number of neutrons by +1.

○

Example: Beta decay of argon-40 will result in chlorine-40 with
the number of neutrons in chlorine to be 23.

Beta Plus Decay Practice

●

Determine the elemental isotope and # of neutrons that is the result
of beta plus decay that emits an electron of the following isotopes.

1.

Carbon-13

2.

Actinium-228

3.

Bismuth-207

4.

Gold-170

5.

Argon-41

6.

Cerium-144

7.

Chlorine-32

8.

Copper-60

9.

S

10.

S

11.

S

12.

S

13.

S

14.

s

Radioactive Decay - Gamma

●

Gamma decay occurs when gamma radiation is emitted from the
nucleus.
○

The nucleus rearranges itself into a lower energy state which
emits gamma radiation.

○

The number of protons and neutrons does not
change.

○

This type of radiation can be
very dangerous because
gamma radiation can go
through most materials.

Fusion

●

Nuclear fusion occurs when 2 or more lighter elements, particularly
hydrogen and helium, fuse together to form a single heavier atom
and releases energy.
○

Energy is only released when elements at iron or lower on the
periodic table are fused together.

○

Therefore, energy is needed to form elements higher than iron on
the periodic table.
■

The amount of protons and neutrons before and after the
reaction stays the same.

Fusion

Hydrogen

●

There are 3 different types of hydrogen:
○

Protium: 1 proton, 1 electron, 0 neutrons

○

Deuterium: 1 proton, 1 electron, 1 neutron

○

Tritium: 1 proton, 1 electron, 2 neutrons

●

Deuterium and tritium are most commonly fused together, releasing
energy and one neutron to make helium.

●

Deuterium can replace one hydrogen atom in water (H2O) to make
heavy water and is fairly common.
○

This means as long as there is water on Earth we potentially
have unlimited energy.

Nucleosynthesis

●

All elements are made by fusion.
○

2 isotopes of hydrogen fuse together to make helium.

○

2 helium fuse together to make beryllium.

○

A hydrogen and helium fuse to make lithium.

○

And so on.

●

These types of reactions don’t happen naturally on Earth.
○

Scientists can make some elements but that requires a big lab.

●

So where do the elements come from?

The Big Bang!

●

Scientists theorized that the universe started as a single point,
expanded, and continues to expand to this day.

●

That single point was hot, dense, and contained particles that we
now know make up the atom.

●

These particles combined to make up the atoms.

●

These atoms combined to make other atoms.

●

These atoms combined to make the first stars and galaxies.

●

These stars combined atoms to make up the first molecules.
○

These new galaxies crashed together and more stars were born
and some died.

Stars

● Stars are where the fun happens.

○ Where atoms combine to make different types of

elements, also called nucleosynthesis.

● But not every type of star can make every element.
● So, let’s first take a look at the different types of stars.

Stars

Supernova

Main-sequence

Red Supergiant

White Dwarf

Red Giant

Life Cycle of Stars

●

A stellar nebula (cloud of gasses and particles) condense and
forms either an average star or a massive star.
○

Both average and massive stars will begin to use its supply of
hydrogen and helium. The more massive the star the faster the
supply is used up. Our sun will burn for about 10 billion years.
■

However, if the star does not have enough mass, fusion
never takes off and the star becomes a brown dwarf.

●

As the supply of hydrogen and helium is used up the star becomes
either a red giant (average) or a red supergiant (massive).

Life Cycle of Stars

●

Red giants and supergiants are dying stars that expanded and began
gobbling up everything in their path.
○

Red giants continue on through death to become a white dwarf, a
dead star that has collapsed in on itself, no longer doing
nucleosynthesis.

○

A red supergiant on the other hand has a more notable ending.
■

A red supergiant goes supernova. This is where elements
higher than iron and nickel are formed because an input of
energy is needed to form these elements, which happens
during the supernova phase.

Life Cycle of Stars

● Once the supernova explodes all the elements that were

made are expelled out into the universe to one day be
made into planets and life forms like us.

○ You are literally made of stardust!

● The core of the star must be 15,000,000oC to begin

making elements.

○ This means that nuclear reactions must be the driving

force for energy in the sun, not chemical reactions.

Life Cycle of Stars

Nasa

Amount of Hydrogen and Helium

●

All of the elements are made in the core of stars, which also
releases energy and light.

○

The light that is produced by nucleosynthesis in the sun is
extremely important to life on Earth.

●

Stars begin with about 75% hydrogen and 25% helium.

○

As stars begin the process of nucleosynthesis the amount
of hydrogen and helium begin to decline.

■

The older the star is the less hydrogen and helium is in
the core and more elements made by nucleosynthesis.

Which Stars Make Which Element