An atom consists of a dense nucleus containing protons and neutrons surrounded by a cloud of electrons. The nucleus contains protons which have a positive charge and neutrons which have a neutral charge. Electrons orbit the nucleus and have a negative charge. The atomic number represents the number of protons in an atom's nucleus, while the mass number is the total number of protons and neutrons.

1. The parts of an Atom

2. The atom
An Atom: The most basic unit of
matter.
An atom has a dense nucleus and a
cloud of negatively charged electrons
around it.
If matter is what everything is made of, and
matter is made of atoms…
Then, everything is really made of atoms!

3. An Electron
Electron: A subatomic particle with a
negative electrical charge.
An electron’s mass is so small that it is
generally not even considered.

4. A Nucleus
Nucleus: The dense center of an atom
containing protons and neutrons.
Nucleus

5. A Proton
A Proton: A subatomic particle within
the nucleus of an atom that has a
positive charge.

6. Neutron
A Neutron: A subatomic particle within
the nucleus of an atom that has a
neutral charge.

7. Energy Level
The energy level of an atom is as
follows:
2,8,8
The first shell has two electrons
The second shell has 8 electrons
The third shell has 8 electrons
MEMORIZE: 2,8,8!!!!!!!!!!

8. Atomic Number
The atomic number is
the number mainly
associated with the
element and represents
the number of protons
present in the atom.

9. Mass Number
The total number of
protons and neutrons.
The mass of an atom
comes from the protons
and neutrons.
Therefore, the mass
includes the masses of
each added together.
This number can be found Mass Number
at the bottom, typically.

10. Atomic Mass
Sub atomic particles are measured in
AMU’s. AMU stands for Atomic Mass
Unit.
Every proton has a mass of 1 AMU
Every Neutron has a mass of 1 AMU
Remember, electrons don’t have a
measureable mass.

11. Element
A pure chemical substance consisting
of ONE type of atom.