UNIT 01
Atomic Structure
Everything in the electrical world starts with matter.
Matter is made of atoms, and atoms contain the particles
that make electrical behavior possible.
In this unit, you will study how atoms are structured,
how electrons behave, and why electrons are so important
to electricity.
THE ATOM
What Is an Atom?
An atom is the basic unit of an element. Every material
is made from atoms.
An atom contains a small, dense nucleus surrounded by
electrons. The nucleus contains protons and neutrons.
The arrangement and number of these particles determine
the identity and electrical properties of the atom.
ATOMIC PARTICLES
The Three Basic Particles
Proton
A proton has a positive electrical charge and is
located inside the nucleus. The number of protons
determines which element the atom is.
Neutron
A neutron has no electrical charge and is located
inside the nucleus. Neutrons contribute to the
atom's mass.
Electron
An electron has a negative electrical charge and
exists around the nucleus. Electrons are especially
important in electrical circuits because moving
electrons produce electric current.
ATOMIC STRUCTURE
Nucleus and Electron Shells
The center of an atom is called the nucleus. The nucleus
contains protons and neutrons.
Electrons occupy regions around the nucleus commonly
described as electron shells or energy levels.
The electrons in the outermost occupied shell are called
valence electrons. These electrons are especially
important when studying electrical conductivity.
ATOMIC NUMBER
Identifying an Element
Atomic Number
The atomic number is the number of protons in
the nucleus of an atom. This number identifies
the element.
Neutral Atom
A neutral atom has the same number of protons and
electrons, so its positive and negative charges
balance.
Ion
An atom becomes an ion when it gains or loses
electrons, giving it a net electrical charge.
VALENCE ELECTRONS
Why Outer Electrons Matter
Valence electrons are the electrons in the outermost
occupied energy level of an atom.
These electrons play an important role in how atoms
interact with one another and how materials conduct
electricity.
In electrical work, understanding valence electrons helps
explain why materials such as copper conduct electricity
well while materials such as rubber resist the movement
of electrons.
ELECTRICAL CONNECTION
Conductors vs. Insulators
Conductors
Conductors allow electric charge to move relatively
easily. Copper and aluminum are common electrical
conductor materials.
Insulators
Insulators strongly resist the movement of electric
charge. Rubber, plastic, and glass are examples of
insulating materials.
ELECTRICAL CONNECTION
From Atoms to Electricity
Electricity is closely connected to the behavior of
electrons.
When electrons move through a conductive material, their
movement is associated with electric current.
Remember This
Atoms contain electrons. Electrons can move through
conductive materials. The movement of electric charge
is what makes electric current possible.
KEY TERMS
Atom
The basic unit of an element.
Proton
Positively charged particle in the nucleus.
Neutron
Neutral particle in the nucleus.
Electron
Negatively charged particle surrounding the nucleus.
Valence Electron
An electron in the atom's outermost occupied shell.
Atomic Number
The number of protons in an atom's nucleus.
KNOWLEDGE CHECK
Which atomic particle is most directly involved in the
movement of electric current through a conductor?
The electron. Electrons carry negative electric charge,
and their movement through a conductive material is
associated with electric current.
