Chemistry 2022-2023
Unit 2: The Structure of the Atom
Section IV
CHAPTER 4: The Structure of the Atom
Section IV Lesson Notes

substances spontaneously
Radioactivity: ___________________________________________________________________________________
emitting radiation
➢
Radiation: lightwave
➢
Nuclear Reaction:
Crays and
1)
a
elementinto
one
change
in
an
atom's
nucleus
another elements
Radioactive Decay
energy by
unstable nuclei
losing
2) Anucleus
D
3)
emitted)
reaction thatinvolves
canchange

particles
Unstable
an atom
elements
radioactive
elements
in
a
spontaneous
radioactive decay
undergo
1. Alpha particles
Radiation
Type
radiation
process
into differentnuclei
splits
of
emitting
thus
2. Beta particles
forming
stable
nonradioactive
3. Gamma Rays
accounts
+
its
Definition
charged particles
in
escharged particles
alpha radiation
high energy
with
radiation
Beta
in
radiation
are
no
mass
for
the
and
lost
neutral.
of
most
energy
during
radioactive
decay
Symbol
↓
of
#
He
Mass (amu)
or
a
4. 0OIS
Mass (kg)
pi2
n
= 2
:
radiation
⑮40
Gamma
rays
1
of
up
a
radiation
O
-
negative charge
with
no
of
0
positively charged particles
radiation thathas
i
clots
⑧
amu
29kg9.109x10-bg
high energy
:
B
or
2+
Alpha radiation made
y
-
e
amu
6.642x10-
Charge
Beta
of
#
mass
called
and emits
and
are
alpha particles.
beta
neutral
particles
energy
Chemistry 2022-2023
Unit 2: The Structure of the Atom
Section IV
Practice
1. Explain radioactivity by completing the paragraph below.
rearranged
↓
identities
↓
affects
/
electrons
/
nuclei
↓
nuclearIreactions
unstable ↓nuclei
unstable ↓
nuclei
radiation
↓
changes
↓
/
identities
/
radiation
↓ decay
radioactive
different element
identities
In chemical reactions, atoms may be _______________,
but their _______________
do not
rearranged
affects
electrons
change. The rearrangement _______________
only the _______________
of the atoms, not the
Noclear reactions are different. In nuclear reactions, _______________
unstable nuclei
nuclei
_______________.
_______________
gain
radiation
stability by emitting _______________.
As a result of _______________
in the nuclei, the atoms’
change
identifies
Unstable nuclei
radiation
_______________change.
_______________
will continue emitting _______________,
in a process
radioactive decay , until stable nuclei, often of a _______________,
differentelement are formed.
called _______________
2. Sequence the steps of a nuclear reaction.
4
______
A stable, nonradioactive atom is formed.
*
2
______
Radiation is emitted.
3
______
The process of radioactive decay continues until the nucleus is stable.
1
______
An atom has an unstable nucleus.
3. Discuss why some elements are radioactive while most elements are not.
Elements with
radioactive
Due
to the
stable.
higher atomic # chigher than
because
they
have
instability, they
nucleiso
undergo
lead pb Atomic as tend to be
big
they
that
radioactive decay
are
until
fairly
unstable.
they
become