Protons neutrons
atomic symbol
atomic number
chemical element
Atoms are tiny pieces of matter that make up all the substances around you. All atoms
contain one or more positively charged particles called
, which are
found in an atom's nucleus. In many atoms, the nucleus also contains
which have no electrical charge. There are also small, negatively
charged particles called electrons found outside the nucleus. Together, these three types
of particles make up the structure of atoms.
The number of protons in an atom is the atom's
When two atoms
have the same atomic number, they are are classified as the same
All known chemical elements are listed in the periodic table, where they are arranged by
atomic number. The periodic table contains information about each element, often
including a short version of the element's full name called its