The atom is a basic unit of matter that consists of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positivelycharged protons and electrically neutral neutrons. The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming amolecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive or negative charge and is an ion. An atom is classified according to the number ofprotons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determines the isotope of the element.
2.- 3 main Subatomic particles(names, location, symbols) 
In physics or chemistry, subatomic particles are the small particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which arenot made of other particles, and composite particles. Particle physics and nuclear physics study these particles and how they interact.
The electron is a subatomic particle carrying a negativeelectric charge. It has no known components or substructure, and therefore is believed to be an elementary particle.
The neutron is a subatomic particle with no net electric charge and a massslightly larger than that of a proton. They are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The numberof protons in a nucleus is the atomic number and defines the type of element the atom forms.
The proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in thenucleus of each atom, along with neutrons, but is also stable by itself and has a second identity as the hydrogen ion, H+. It is composed of three fundamental particles: two up quarks and one down...