![Corner icon for tutorials on atoms. Atoms Chalkboard](../art_global/board-atom.png)
Atoms Are Building Blocks
![Atoms are made of electrons, neutrons, and protons. Image showing an atomic nucleus with protons and neutrons. Electrons spin around the nucleus in a variety of directions.](art/atom-struct-01.png)
Atoms are the foundation of chemistry. They are the basis for everything in the Universe. As you know, matter is composed of atoms. Solids are made of densely packed atoms while gases have atoms that are spread out. We're going to cover basics like atomic structure and bonding between atoms. As you learn more, you can move to the reactions and biochemistry pages and see how atoms form compounds that help the biological world survive.
Are there pieces of matter that are smaller than atoms? Sure there are. Super-small particles can be found inside the pieces of atoms. These subatomic particles include nucleons and quarks. Nuclear chemists and physicists work together at particle accelerators to discover the presence of these tiny, tiny, tiny pieces of matter. However, science is based on the atom because it is the smallest distinct unit of matter.
Three Easy Pieces
![Electrons orbit the atomic nucleus where you find protons and neutrons. Simple image showing classic structure of an atom with a neutron and proton in the nucleus and an atom in orbit.](art/atom_struct1.png)
There are almost 120 known elements in the periodic table. (117 as we write this) Chemists and physicists are trying to make new ones every day in their labs. The atoms of different elements have different numbers of electrons, protons, and neutrons. Every element is unique and has an atomic number. That number tells you the number of protons in every atom of the element. The atomic number is also called the proton number.
Charges of Atoms
![Protons carry a positive charge, neutrons carry a neutral charge, and electrons carry a negative charge. THree subatomic particles showing a large neutron with a neutral charge, large proton with a positive charge, and a small electron with a negative charge.](art/atom_structure3.png)
The electron always has a "-", or negative, charge. The proton always has a "+", or positive, charge. If the charge of an entire atom is "0", or neutral, there are equal numbers of positive and negative charges. Neutral atoms have equal numbers of electrons and protons. The third particle is the neutron. It has a neutral charge, also known as a charge of zero.
Since the number of protons in an atom does not change, fewer or extra electrons can create a special atom called an ion. Cations have fewer electrons and have a positive charge. Anions have extra electrons that create a negative charge.
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