Download Chapter 2, section 4 Formation of Elements

Think – Don’t Speak.
What does it mean to fuse
something together?
When hear word fission – what
does it mean?
I. How Elements Form
A. Nuclear Fusion – when two atomic
nuclei combine
1. energy is released
2. a new element is formed
Video: How are Elements Formed?
www.youtube.com/watch?v=neMEo8ZrwuI
II. Fusion in Stars
A. Stars begin as hydrogen atoms, the
H fuses to make heavier elements.
B. Energy is given off in light, heat, and
radiation.
http://www.youtube.com/watch?v=neMEo8ZrwuI
5 min clip
Alpha, Beta, and Gamma Decay
The Atom
The atom consists of two parts:
1. The nucleus which contains:
protons
neutrons
2. Orbiting electrons.
The mass of an atom is almost entirely due
to the number of protons and neutrons.
= number of protons +
Mass number
number of neutrons
A
X
Z
Element symbol
Atomic number
=
number of protons
A
X
Z
Mass #
--- Atomic #
#neutrons
Mass # = number of protons + number of neutrons
Atomic # = number of protons
There are many types of uranium:
235
U
92
ISOTOPES
238
U
92
Mass #
Mass #
Atomic #
Atomic #
Number of protons
Number of protons
Number of neutrons
Number of neutrons
Number of electrons
Number of electrons
There are many types of uranium:
235
238
U
92
2+
U
92
Mass #
235
Mass #
238
Atomic #
92
Atomic #
92
Number of protons
92
Number of protons
92
Number of neutrons
143
Number of neutrons
146
Number of electron
92
Number of electron
90
Most of the isotopes which occur naturally
are stable.
A few naturally occurring isotopes and all
of the man-made isotopes are unstable.
Unstable isotopes can become stable by
releasing different types of particles.
This process is called radioactive decay
and the elements which undergo this
process are called radioisotopes/.
Radioactive Decay
Radioactive decay results in
the emission of either:
• an alpha particle (a),
• a beta particle (b),
• or a gamma ray (g).
Alpha Decay
An alpha particle is identical to
that of a helium nucleus.
It contains 2 protons
and 2 neutrons.
Alpha Decay
222
226
Ra
88
Rn
86
4
He
2
Alpha Decay
A
A-4
4
226
222
4
X
Z
Ra
88
Y
+
Z-2
Rn
+
86
He
2
He
2
Alpha Decay
222
Rn
86
222
Rn
86
A
4
Y
He
+
Z
2
218
Po
+
84
4
He
2
Alpha Decay
A
230
4
234
230
4
X
Z
U
92
Th
He
+
90
2
Th
He
+
90
2
Alpha Decay
230
Th
90
230
Th
90
A
4
226
4
Y
He
+
Z
2
Ra
He
+
88
2
Beta Decay
A beta particle is a fast moving electron
which is emitted from the nucleus of an
atom undergoing radioactive decay.
Beta decay occurs when a neutron changes
into a proton and an electron.
Beta Decay
As a result of beta decay, the nucleus
has 1 less neutron, but 1extra proton.
The atomic number, increases by 1 and
the mass number, stays the same.
Beta Decay
218
218
Po
84
At
85
b
-1
0
Beta Decay
A
X
Z
218
Po
84
A
b
-1
218
b
-1
Y
+
Z+1
At
+
85
0
0
Beta Decay
234
A
b
-1
234
234
b
-1
Th
90
Th
90
Y
+
Z
Pa
+
91
0
0
Beta Decay
A
210
b
-1
210
210
b
-1
X
Z
Tl
81
Pb
+
82
Pb
+
82
0
0
Beta Decay
210
A
b
-1
210
210
b
-1
Bi
83
Bi
83
Y
+
Z
Po
+
84
0
0
Gamma Decay
Gamma rays are not charged particles like a
and b particles.
Gamma rays are electromagnetic radiation
with high frequency.
When atoms decay by emitting a or b
particles to form a new atom, the nuclei of
the new atom formed may still have too
much energy to be completely stable.
This excess energy is emitted as gamma
rays
III. Synthetic Elements by Humans
A. Synthetic Element – human-made, not formed
in nature.
B. Natural Element – forms by natural processes
Synthetic Elements
C. Synthetic elements are made by smashing
atoms together in a particle accelerator.