Atoms are small units of matter that cannot be further broken down through chemical reactions with the exception of removal or addition of electrons. An atom is made up of three subatomic particles: Electrons, Protons, and Neutrons. Atoms are sometimes considered the "building blocks" of matter.

Atomic Structure[]

The center of the atom is made up of the protons and neutrons. This is called the Nucleus (Plural form Nuclei (Noo-Klee-Ide)).  Since protons are said to be positively charged particles, the nucleus is always positively charged.  One element is different from another because of the number of protons in its nucleus.

Electrons, which are negatively charged particles, orbit the positively charged nucleus at different energy levels.

 When two atoms of different atoms come together, they form Compounds, bonding to each other very tightly.


Atoms are incredibly small, they cannot be seen even the most powerful microscope. The size of the smallest atom - hydrogen atom, has a radius of 32 pm (3.2 × 10−13 m).

Unstable Nuclei[]

Certain Atoms are Unstable, and spontaneously emit different particles. (See Radioactivity)

Elements & Isotopes[]

Different Atoms are atoms of different element. For instance, one proton and one electron are Hydrogen-1, while fifty one protons & electrons and one-hundred and twenty two neutrons is Antimony. Things can get even more complicated, though, as the number of neutrons in an atom decides what Isotope it is. So while Hydrogen-1 has 1 Proton and 1 electron, Hydrogen-2 has 1 proton, 1 electron, and 1 neutron. every isotope of an element has the same number of protons and electrons, but differing numbers of Neutrons.