An atom is the smallest unit of an element and consists of a central nucleus surrounded by electrons. The nucleus is composed of protons and neutrons and contains most of an atom's mass. Protons are positively charged particles found in the nucleus, neutrons are uncharged particles in the nucleus, and electrons are negatively charged particles located in shells surrounding the nucleus.

1. ATOMS AND ATOMIC
STRUCTURE
Atom Nucleus Proton Neutron Electron

2. WHAT IS AN ATOM?
o The smallest unit of
an element.
o Consists of a
central nucleus
surrounded by one
or more electrons.

3. WHAT IS THE NUCLEUS?
o The central part of
an atom.
o Composed of
protons and
neutrons.
o Contains most of an
atom's mass.

4. WHAT IS A PROTON?
o Positively charged
particle.
o Found within an
atomic nucleus.

5. WHAT IS A NEUTRON?
o Uncharged particle.
o Found within an
atomic nucleus.

6. WHAT IS AN ELECTRON?
o Negatively
charged particle.
o Located in shells
that surround an
atom's nucleus.

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