1) The formation of heavier elements occurs through nuclear fusion reactions during stellar evolution and supernova explosions. 2) Elements up to iron are formed through fusion in stars, while elements heavier than iron are formed through fusion and neutron capture processes during supernovae. 3) Key nuclear fusion reactions in stars include the proton-proton chain, triple alpha process, CNO cycle, and alpha ladder, which fuse hydrogen and helium into heavier elements up to iron.

1. (Formation of the Heavy Elements)

2. CONTENT How the elements found in the universe were formed
CONTENT
STANDARD
At the end of the lesson, you will be able to demonstrate an
understanding of:
1. the formation of the elements during the Big Bang and during
stellar evolution
2. the distribution of the chemical elements and the isotopes in
the universe
LEARNING
COMPETENCIES
At the end of the lesson,
1. Give evidence for and describe the formation of heavier
elements during star formation and evolution
(S11/12PS-IIIa-2)
2. Write the nuclear fusion reactions that take place in stars
that lead to the formation of new elements
(S11/12PS-IIIa-3)
3. Describe how elements heavier than iron are formed
(S11/12PSIIIa-b-4))

3. RECALL

4. Cosmic ray spallation is a form of naturally occurring nuclear fission and
nucleosynthesis. It refers to the formation of chemical elements from the
impact of cosmic rays on an object.

8. Summary:
Sagan covers several topics, and focusses
mainly on the possibility of extraterrestrial
intelligence, the likelihood of the existence
of more advanced civilizations, and their
distribution in the local galaxy, and in the
universe. He describes the hypothetical
opinions of more advanced intelligences
and their views of the Earth, as well as
communication with mankind. He also
discusses the popularity of UFO sightings
and attempts mathematically to portray
the probability of such events. Sagan also
discusses his view of astrology as a
pseudoscience.

9. 1) Fusion -
2) Isotope -
3) Stellar evolution -
4) Stellar nucleosynthesis -
5) Supernova
nucleosynthesis -
6) Proton-proton chain
reaction -
7) Triple alpha process
nucleosynthesis -
8) Alpha ladder -
9) CNO cycle -
10) Main-sequence star -
11) Red giant -
12) Supernova explosion -
13) Supernova -
14) R-process -
15) S-process -
KEY TERMS

10.  is the
combining of
nuclei to form a
bigger and
heavier
nucleus.

11.  is a form of a chemical
element whose atomic
nucleus contains a specific
number of neutrons, in
addition to the number of
protons that uniquely
defines the element.

12.  is the process
by which a star
changes over the
course of time.

16.  is the process by which the
natural abundances of the
chemical elements within stars
vary due to nuclear fusion
reactions in the cores and
overlying mantles of stars.

18.  is a theory of the production
of many different chemical
elements in supernova
explosions, first advanced by
Fred Hoyle in 1954.

20.  is one of the two (known) sets of
fusion reactions by which stars
convert hydrogen to helium. It
dominates in stars the size of the
Sun or smaller.

22.  is a set of nuclear fusion reactions
by which three helium-4 nuclei
(alpha particles) are transformed
into carbon.

24.  is one of two classes of nuclear
fusion reactions by which stars
convert helium into heavier
elements, the other being the
triple-alpha process.

26. (for carbon–nitrogen–oxygen)
is one of the two known sets of
fusion reactions by which stars
convert hydrogen to helium.
It is a catalytic cycle.

28. is any star that is fusing
hydrogen in its core and has a
stable balance of outward
pressure from core nuclear
fusion and gravitational forces
pushing inward.

30. is a dying star in the last
stages of stellar evolution.

32. is the explosion
of a star
the largest
explosion that
takes place in
space.

34. Rapid
neutron capture process
 involves rapid capture of neutrons by the
atom.
 is a set of reactions in nuclear astrophysics
that are responsible for the creation
(nucleosynthesis) of approximately half the
atomic nuclei heavier than iron.

35. Slow
neutron capture process
involving slow neutron capture
in red giants.
 is a series of reactions in nuclear astrophysics which
occur in stars, particularly AGB stars. It is responsible
for the creation (nucleosynthesis) of approximately half
the atomic nuclei heavier than iron.

39. ACTIVITY