Atoms

Atoms are made of particles.
In the center--the NUCLEUS--of an atom are positively charged particles called PROTONS.
PROTONS are often represented by a plus sign +

In the nucleus of an atom are also particles called NEUTRONS.
NEUTRONS are neutral--they have no electrical charge. They are often represented by a zeror 0.

These two kinds of particles are subject to THE STRONG NUCLEAR FORCE that makes them stick to each other.

NEUTRONS and PROTONS are examples of HADRONS, particles that are affected by THE STRONG NUCLEAR FORCE.

Spinning around the nucleus of an atom are negatively charged particles called ELECTRONS.
ELECTRONS are often represented by a minus sign -

ELECTRONS are LEPTONS, particls that are NOT affected by the STRONG NUCLEAR FORCE.

+0-
Hydrogen atoms have one proton and one neutron in the nucleus and one electron spinning around it.

++00--
Helium atoms have two protons and two neutrons in the nucleus and two electrons spinning around it.
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HOW MANY PROTONS ARE THERE IN THE NUCLEUS OF AN ATOM OF OXYGEN?