Download o Atomic Number = Protons = Electrons o Mass – Atomic Number

STAAR REVIEW—PARTS OF AN ATOM—CATEGORY 1
• There are 3 subatomic particles in an atom:
PARTICLE
Protons
Neutrons
Electrons
CHARGE
Positive (+)
Neutral/None
Negative (-)
LOCATION
Nucleus
Nucleus
Electron Cloud
http://chemistry.tutorvista.com/nuclear-chemistry/properties-of-subatomic-particles.html
•
A=P=E M-A=N
MASS
1 amu
1 amu (same as protons)
None (.000543 amu)
Valence Electrons
are electrons in the outermost
energy level of an atom (Carbon
has 4 valence electrons).
All elements in the same
group/column on the Periodic
Table have the same number of
valence electrons and therefore
similar properties and reactivity.
These are the electrons
specifically involved in
forming chemical bonds.
o Atomic Number = Protons = Electrons
o Mass – Atomic Number = Neutrons
• OTHER KEY POINTS TO REMEMBER:
o The overall charge of a stable atom is zero because the number of protons
and electrons are equal (Always assume the number of protons and electrons
are equal unless you are told differently!).
o The charge of an atom’s nucleus is always positive due to the protons it
contains (Carbon’s nucleus has a +6 charge due to its 6 protons) even though
its overall charge is still zero.
o Protons give an element its identity (Without being told, we could count the
protons on the above atom (6), find the element with the atomic number of 6
(using our A=P=E rule) and determine that it is an atom of Carbon).