An atom is the smallest unit of matter. An element is made up of the same kind
of atom, and cannot be broken down any further. (Example: The element
Hydrogen is made up of Hydrogen atoms).
An atom consists of smaller particles called subatomic particles: protons, electrons
and neutrons. The centre of the atom is called the nucleus and is made up of
protons and neutrons. Around the nucleus are shells and electrons move around
these shells.
Orbit/Shell
Nucleus
Electron
Summary:
Particle
Proton
Electron
Neutron
Symbol Mass
P
1u
e
1/2000 u
Charge
Positive (+1)
Negative (-1)
n
Neutral (0)
1u
Location
Inside the nucleus
Orbits outside of the
nucleus
Inside the nucleus
When you look at a box on the periodic table, it generally has this appearance:
Atomic Number
Symbol of the Element
Element Name
Atomic Mass
 Atomic Number = Number of Protons
 Each element has their own identity, because each element’s atoms have their
own atomic number
Atoms are neutral and have no charge, because the
# of Protons = # of Electrons
Since protons and neutrons are the only particles with a larger mass, the mass of
an atom is determined by the number of protons and neutrons.
Atomic Mass = # of Protons + # of Neutrons
# of Neutrons = Atomic mass - # of Protons
Standard Atomic Notation is a way to show the element symbol, atomic number
and atomic mass of an element.
Ex. The Standard Atomic Notation for Helium looks like this:
Rounded Atomic Mass
4
Atomic Number
2
He
Homework: Standard Atomic Science Chart
Read Page 234-235 Page 240 #1-6