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Atoms and Bonding
Big Idea and Essential Questions
The atomic structure of an element determines
how element interacts with other elements.
Lesson 1 – The Atom: How do we know what
parts make up the atom?
Lesson 2 – The Periodic Table: How are
elements arranged on the periodic table?
Lesson 3 – Electrons and Chemical Bonding:
How do atoms interact with each other?
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Atoms and Bonding - Elements and Atoms
The Building Blocks of Matter
Matter may consist of elements, compounds, or mixtures.
Compound: a pure substance made of 2 or more elements that
are chemically combined. (Hydrogen and Oxygen: H2O)
Elements:
simple pure
substances.
Contains only 1
type of atom.
Aluminum: Al
Mixture: 2 or more substances that are not
chemically combined. Sand, Gravel, Shells
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Atoms and Bonding
P158-159
What makes up matter?
• The Greek philosopher Democritus thought
matter could be divided into smaller units until
you obtained a particle that could not be cut.
• He called this particle atomos, meaning “not
able to be divided.”
• An atom is the smallest particle into which an element
can be divided and still be the same element.
• Scientists now know that atoms are made of even
smaller particles, but the atom is the smallest unit that
has the chemical properties of an element.
• There are many types of atoms that combine in
different ways to make all substances.
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Atoms and Bonding
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Atoms and Bonding - Elements and Atoms
P160-161
Who developed the atomic theory?
John Dalton (1808) thought that atoms were like smooth, hard
spheres that could not be broken into smaller pieces.
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Atoms and Bonding - Elements and Atoms
P160-161
Who developed the atomic theory?
J.J. Thomson (1897) suggested that atoms had
negatively charged particles embedded in a positive
sphere.
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Atoms and Bonding - Elements and Atoms
P160-161
Who developed the atomic theory?
Ernest Rutherford (1908) Gold Foil Experiment led him to propose
an atomic model with a positively charged nucleus - a small,
dense center that has a positive charge.
Electrons (negative) moved around a small, positively charged
nucleus in the center of the atom. He named the positively charged
particles Protons.
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Atoms and Bonding - Elements and Atoms
P160-161
Who developed the atomic theory?
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Atoms and Bonding - Elements and Atoms
P160-161
Atomic Theory and Models
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Atoms and Bonding
What is the current atomic theory?
• In 1932, James Chadwick discovered
that the nucleus contains uncharged
particles called neutrons.
• In the current atomic theory, electrons
do not move in circular paths around
the nucleus as Bohr thought.
• Instead, the current theory suggests
that electrons move within an area
around the nucleus called the
electron cloud.
Atoms and Bonding
Up and Atom!
What are the parts of an atom?
• Atoms are made up of protons, neutrons, and
electrons.
• Protons are the positively charged particles
of atoms. The relative charge of a single
proton is written as 1+.
• In the unified atomic mass unit (u), the mass
of a proton is about 1 u.
Atoms and Bonding
What are the parts of an atom?
• Neutrons are particles that have no electrical
charge.
• The mass of a neutron is slightly more than
that of a proton, but it is still close to 1 u.
• Most atoms contain at least as many neutrons
as protons.
Atoms and Bonding
What are the parts of an atom?
• Together, protons and neutrons form the
nucleus of the atom.
• The overall charge of the nucleus is equal to
the charge on the total number of protons in
the nucleus.
• The nucleus is small but very dense.
Atoms and Bonding
What are the parts of an atom?
• The negatively charged particles of an atom
are called electrons. The charge of a single
electron is represented as 1-.
• It is not possible to determine the exact
position and speed of an electron at the same
time.
• So we picture the electrons as being in an
electron cloud around the nucleus.
Atoms and Bonding
What are the parts of an atom?
• Compared with protons and neutrons,
electrons have very little mass.
• The number of protons and electrons in an
atom are the same, so their charges are
balanced and the atom has an overall charge
of 0.
• An atom can gain or lose electrons to become
an ion, which has a net positive or negative
charge.
Atoms and Bonding
Parts of an atom
Part of the
atom
Location
Electric
charge
Relative
mass
Proton
Nucleus
1+
Slightly less
massive than
a neutron
Neutron
Nucleus
0
Slightly more
massive than
a proton
Electron
Electron
cloud
1-
Almost 0
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Atoms and Bonding
Take a Number!
How can we describe atoms?
• Different combinations of protons, neutrons, and electrons
produce atoms with different properties.
• The number of each kind of particle within an atom
determines its unique properties.
• These different atoms combine to form the different
substances all around us.
• The number of protons distinguishes the atoms of one
element from the atoms of another.
• The number of protons in the nucleus of an atom is the
atomic number of that atom.
• The total number of protons and neutrons in an atom’s
nucleus is its mass number.
Atoms and Bonding
How can we describe atoms?
Atomic Number = # of Protons = # of electrons
Atomic Mass = # of Protons + # of neutrons
(Mass Number)
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Atoms and Bonding How can we describe atoms?
Unit 3 Lesson 1 The Atom
Isotopes?
• The atoms of a certain element always have the same
number of protons, but the number of neutrons may differ.
• Isotopes are atoms of the same element that have different
numbers of neutrons.
• The total number of protons and neutrons in an atom’s
nucleus is its mass number.
Atomic Mass –
Average Mass of
an element
(decimal). Includes
# of protons and
neutrons and
isotopes
Atoms and Bonding
How can we describe atoms?
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Atoms and Bonding
How can we describe atoms?
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Atoms and Bonding
How can we describe atoms?
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Atoms and Bonding
How can we describe atoms?
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Atoms and Bonding
The Atom WS
Vital Statistics for Common Elements
Element
Protons
Neutrons
Hydrogen
1
0
Helium
2
Beryllium
2
4
Carbon
6
6
Nitrogen
7
7
Oxygen
8
Fluorine
9
11
8
10
Sodium
5
12
Electrons
Atomic
Number
1
2
1
Mass
1
2
4
4
4
9
6
7
8
9
11
6
7
8
12
9
19
11
23
14
16
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