After
reading this section you will be able to do
the following:
Describe
the basic structure of an atom.
Explain
what holds an atom together.
What
is an atom composed of?
An atom is the smallest
particle of any element that still retains the characteristics
of that element. However, atoms consist of even smaller particles.
Atoms consist of a central, dense nucleus that is surrounded by
one or more lightweight negatively charged particles called electrons.
The nucleus is made up of positively charged particles called
protons and neutrons which are neutral. An atom is held together
by forces of attraction between the electrons and the protons.
The neutrons help to hold the protons together. Protons and neutrons
are believed to be made up of even smaller particles called quarks.
We will limit our discussions to protons, neutrons and electrons.
Niels Bohr was a Danish
scientist who introduced the model of an atom in 1913. Bohr's
model consists of a central nucleus surrounded by tiny particles
called electrons that are orbiting the nucleus in a cloud.
These electrons are spinning so fast around the nucleus of the
atom that they would be just a blur if we could see particles
that small. In our pictures and exercises the electron appears
to orbit in the same path around the nucleus much like the planets
orbit the Sun. But, please be aware that electrons do not really
orbit in the same path. The electrons actually change their orbit
with each revolution.
Review
Atoms
are composed of protons, neutrons, and electrons.
The forces
of attraction between the electrons and the protons hold an
atom together.
