Download The Structure of an Atom

The Structure of an
Atom
Chapter 4.2
Warm-up:
KWL Chart - ATOMS
What I Know
About Atoms
What I Would
Like to Learn
About Atoms
What I Have
Learned About
Atoms
Properties of Subatomic Particles

There are 3 types of subatomic particles in
an atom
– Protons
– Electrons
– Neutrons
Protons
POSITIVELY charged particle located in
the nucleus of an atom
 Each element contains at least 1 proton
 Each proton has a charge of +1
 Rutherford discovered that the amount of
positive charge varies among elements

Electrons
NEGATIVELY charged subatomic particle
that is found in the space outside the
nucleus
 Each electron has a charge of 1 Its mass is so small that it is not taken
into consideration

Neutrons
Neutral subatomic particle that is found in
the nucleus of an atom.
 Its mass is almost exactly equal to that of
a proton

Comparing Subatomic Particles

Protons, Neutrons, and Electrons can be
distinguished by mass, charge, and location in
the atom
Particle Symbol Relative
Charge
Relative
Mass
Actual
Mass
Electron
e-
1-
1/1836
9.11x10-28
Proton
p+
1+
1
1.674x10-24
Neutron
n
O
1
1.675x10-24
Fun Facts About Atoms
Atomic Number

Atomic number of an element is equal to
the number of protons in the nucleus of
that element
– Atomic number = # protons

Atoms of different elements have different
numbers of protons
Electrically Balanced Atoms
The number of protons in an atom is
balanced by the number of electrons in
the atom so that the atom does not carry
a net charge
 So, the atomic number also tells us the #
of electrons

Mass Number

Mass number = # protons + # neutrons
(in the nucleus of an atom)
Calculating the Number of Neutrons

Number of Neutrons =
Mass number – Atomic Number
Isotopes
Isotopes are atoms of the same element
that have different numbers of neutrons
 Isotopes of an element have the same
atomic number, but different mass
numbers because they have different
numbers of neutrons

More About Isotopes..
Carbon Isotopes