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.
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