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Name_______________________________________________Class______________Date___________ 1
Antonelli – Chemistry –LHWHS 2010-2011
Review Packet – Unit 2 – Intro to Atomic Structure
Review Packet – Unit 2
Intro to Atomic Structure
History of Atomic Theory
1. Compare and contrast Dalton, Rutherford, and Thomson's
theories on atomic structure and the experiments they
used to develop their theories.
You should be able to answer an essay question on this
Dalton's Atomic Theory (early 1800s)
1) All matter is made of atoms. Atoms are indivisible and
2) All atoms of a given element are identical in mass and
3) Compounds are formed by a combination of two or more
different kinds of atoms.
4) A chemical reaction is a rearrangement of atoms.
Thomson - 1897
In 1897, J. J. Thomson dramatically changed the modern view
of the atom with his discovery of the electron. Thomson's
work suggested that the atom was not an "indivisible"
particle as John Dalton had suggested but, a jigsaw puzzle
made of smaller pieces.
Thomson's notion of the electron came from his work with a
nineteenth century scientific curiosity: the cathode ray
tube. For years scientists had known that if an electric
current was passed through a vacuum tube, a stream of
glowing material could be seen; however, no one could
explain why. Thomson found that the mysterious glowing
stream would bend toward a positively charged electric
plate. Thomson theorized, and was later proven correct,
that the stream was in fact made up of small particles,
pieces of atoms that carried a negative charge. These
particles were later named electrons.
Thomson imagined that atoms looked like pieces of plum
pudding, a structure in which clumps of small, negatively
charged electrons (the "raisins") were scattered inside a
smear of positive charges. In 1908, Ernest Rutherford, a
former student of Thomson's, proved Thomson's plum pudding
structure incorrect.:
Name_______________________________________________Class______________Date___________ 3
Antonelli – Chemistry –LHWHS 2010-2011
Review Packet – Unit 2 – Intro to Atomic Structure
Rutherford – 1908
Ernest Rutherford developed his atomic theory describing
the atom as having a central positive nucleus surrounded by
negative orbiting electrons. This model suggested that most
of the mass of the atom was contained in the small nucleus,
and that the rest of the atom was mostly empty space.
Rutherford came to this conclusion following the results of
his famous gold foil experiment. This experiment involved
the firing of radioactive particles through minutely thin
metal foils (notably gold) and detecting them using screens
coated with zinc sulfide. Rutherford found that although
the vast majority of particles passed straight through the
foil approximately 1 in 8000 were deflected leading him to
his theory that most of the atom was made up of 'empty
Rutherford’s theory replaced the previously held “plum
pudding” model of the atom.
Atomic Structure and How We Represent it
2. Be able to determine the number of protons, neutrons
and electrons in an atom given the atom's atomic mass
and atomic number.
atomic number = # of protons
Atomic mass = # protons + # of neutrons
# of neutrons = atomic mass – atomic number
3. Describe the model of the atom, ion, or isotope in
terms of protons, neutrons, and electrons
Neutrons and protons form a dense, positively charged
Electrons are very small negatively charged
particles that move in orbitals surrounding the
these orbitals are often referred to as an
“electron cloud”.
4. Be able to express an atom’s, isotope’s, or ion’s
Name_______________________________________________Class______________Date___________ 5
Antonelli – Chemistry –LHWHS 2010-2011
Review Packet – Unit 2 – Intro to Atomic Structure
composition using the following format:
5. State a relative mass, size, and charge of an
electron, proton, and neutron.
Protons and neutrons have approximately the same mass.
Electrons are about 2000 times smaller than protons or
6. Understand how atomic structure is represented on the
periodic table.
You should be able to find the atomic number and
atomic mass of an element from the periodic table.
7. Identify a given element as a metal or a non-metal
based on it’s location in the periodic table
8. Locate and identify the following groups on the
periodic table:
a. Halogens
b. Alkali Metals
c. Alkaline Earth Metals
d. Transition metals
e. Noble Gases
9. Given the number and kind of atoms that make up a
compound, write the chemical formula it.
Each molecule of this compound contains two hydrogen
atoms and one oxygen molecule
Each unit of this compound has 1 calcium for every 2
Average Atomic Mass
Demonstrate understanding of the difference
between mass number and average atomic mass by
calculating average atomic mass using experimental
Refer to your Pennium lab and isotope homework for
more information on how to do this (it involves
calculating a weighted average)
Compare and contrast the difference in atomic
structure of an ion, isotope, and neutral atom.
Ion = charged particle (atom with different
number of electrons than protons)
Isotope = Atoms of an element with same number of
protons but different numbers of neutrons.
lends a different mass number to each isotope.
Neutral atom = atom with same number of electrons
and protons
Know how to use the terms cation and anion
Cation = positively charged ion
Anion = negatively charged ion
Name_______________________________________________Class______________Date___________ 7
Antonelli – Chemistry –LHWHS 2010-2011
Review Packet – Unit 2 – Intro to Atomic Structure
Be able to predict the ion an atom will most
likely form based on its location in the periodic
Fluorine is in group 17 – thus it is most likely to
gain an electron and form FOxygen is in group 16 – so it is most likely to gain
two electrons and from O2Sodium is in group 1 – so it is most likely to lose
one electron and form Na+
Calcium is in group 2 – so it is most likely to lose 2
electrons and form Ca2+