The Structure of an Atom
Chapter 4.1
Subatomic Particles
1. Subatomic particles include protons,
electrons, and neutrons.
2. Protons
A. A proton is a positively charged subatomic
particle that is found in the nucleus of an
atom.
B. Each nucleus must contain at least one
proton.
C. Each proton is assigned a charge of 1+.
D. Some nuclei contain more than 100
protons.
Subatomic Particles
3. Electrons
A. An electron is a negatively charged
subatomic particle that is found in the space
outside the nucleus.
B. Each electron has a charge of 1-.
4. Neutrons
A. A neutron is a neutral subatomic particle
that is found in the nucleus of an atom.
B. It has a mass almost exactly equal to that
of a proton.
Properties of Subatomic
Particles
Particle
Symbol
Relative
Charge
Relative
mass
(Proton
= 1)
Actual
Mass
(g)
Electron
e-
1-
1/1836
9.11x10-28
Proton
p+
1+
1
1.674x10-24
Neutron
n
0
1
1.675x10-24
Comparing Subatomic Particles
5. Comparing Subatomic Particles
A. Protons, electrons, and neutrons can
be distinguished by mass, charge and
location in an atom.
B. Protons and neutrons have almost the
same mass.
C. According to the relative mass of
electrons in the above table; how many
electrons would it take to equal the
mass of a proton or neutron?
(1/1836)x=1; About 2,000 electrons
Comparing Subatomic Particles
D. Electrons have a charge that is equal in
size but opposite the charge of a proton.
E. Neutrons have no charge.
F. Where are protons and neutrons
found?
•
In the nucleus
G. Where are electrons found?
•
The space outside the nucleus.
Comparing Subatomic Particles
H. Everything scientists know about the
nucleus and subatomic particles is
based on how the particles behave.
We are still unable to see the inside of
an atom. However, we do have
microscope that can show how atoms
are arranged on the surface of a
material.
Atomic/Mass Number
6. Atomic Number and Mass Number
A. The atomic number of an element
equals the number of protons in an
atom of that element.
B. The atoms of any given element
always have the same number of
protons.
C. There is one proton in the nucleus of
every hydrogen atom. What is the
atomic number for hydrogen?
• 1
Atomic/Mass Number
D. Atoms of different elements have
different numbers of protons.
E. What other element have an
atomic number of 1?
•
None, only hydrogen has an
atomic number of 1.
F. Atomic numbers can be used to
refer to elements since they are
unique to that element.
Atomic/Mass Number
G. Each positive charge in an
atom is balanced by a negative
charge because atoms are
neutral.
H. The atomic number of an
element also equals the number
of electrons in an atom.
Mass Number
7. Mass Number
A. The mass number of an atom is the
sum of the protons and neutrons in
the nucleus of that atom.
B. You can find the number of
neutrons by subtracting the atomic
number from the mass number.
C. number of neutrons = mass
number - atomic number
Fill in the table about the nucleus of
these atoms.
Element
Lithium
Oxygen
Boron
Neutrons
Protons
Mass #
Atomic #
Fill in the table about the nucleus of
these atoms.
Element
Neutrons
Protons
Mass #
Atomic #
Lithium
4
3
7
3
Oxygen
8
8
16
8
Boron
6
5
11
5
Fill in the table about these atoms.
Element
Sulfur
Iron
Silver
Hydrogen
Aluminum
Atomic #
Mass #
Neutrons
Protons
Electrons
Fill in the table about these atoms.
Element
Atomic #
Mass #
Neutrons
Protons
Electrons
Sulfur
16
32
16
16
16
Iron
26
56
30
26
26
Silver
47
108
61
47
47
Hydrogen
1
1
0
1
1
Aluminum
13
27
14
13
13
Isotopes
8. Isotopes
A. Isotopes are atoms of the same
element that have different numbers of
neutrons and different mass numbers.
B. Isotopes of an element have the same
atomic number but different mass
numbers because they have different
numbers of neutrons.
Isotopes
Ex. 1) Oxygen has 8 protons and 8
neutrons with a mass number of 16.
An isotope of oxygen may have 8
protons and 9 neutrons with a mass
number of 17.
Isotopes
C. These isotopes are referred to by their
mass number.
Ex. 2) Oxygen-16, Oxygen-17
D. Since hydrogen-1 has no neutrons and
one proton adding a neutron doubles its
mass.
E. Water that contains hydrogen-2 atoms
in place of hydrogen-1 atoms is called
heavy water