Name:______________________________________ Period _______ Date _______________________
Section 3.2 Practice Worksheet A
The Discovery of the Subatomic Particles of the Atom
Part 1
In Section 3.2 we learn that the atom (the smallest unit of an ______________) is comprised of three
fundamental subatomic particles: the _________________ , _____________, and________________ .
 The proton is the entity that determines the ________________ of an atom. If two atoms have a
different number of protons then we know that they must represent different elements. Protons
are __________________ charged and found in the nucleus.
o How do we determine the number of protons in an atom?

An electron in an atom is equal in magnitude to a proton, but _______________ charged. If an
atom is neutral the number of electrons will ________________ the number of protons.
o What do we call an atom that has more or less electrons than protons?
o What are the two types of these called?

The neutron is a _______________ particle in the nucleus of an atom. Protons and neutrons
have a relative mass number of _______ . When you add the number of neutrons and protons in
an atom we are calculating the ____________________ .
o So how do we determine the number of neutrons in an atom?
o What do we call atoms of the same element that have different number of neutrons?
Review:
What was J.J. Thomson’s contribution to the atom?
What was Rutherford’s contribution to the atom?
Part 2 – Representing Atoms, Ions and Isotopes
In chemistry, information about the number of subatomic particles in atom can be represented in two
basic forms:

Isotope notation shows the element name and mass number of an atom
o Ex:

Nuclear notation shows the element symbol, atomic number, and mass number. It will also
indicate if a charge is present (thus, making it an ion)
Charge, if present