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Atomic Structure Study Guidegenchemand ap

Atomic Structure Study Guide
Due: Oct. 22nd
1. a. Identify the main points of John Dalton’s Atomic Theory.
 Atoms are the building block of all matter
 Atoms are indivisible (indestructible).
 Atoms of the same element behave the same.
 When elements combine chemically, they combine in a fixed composition or
predictable way.
 Atoms are preserved during physical and chemical changes. In chemical changes,
compounds might be destroyed but the atoms composing the compound is
preserved. They just rearranged to produce something new. After further
research this became a law: Law of Conservation of Matter.
b. Which one of his points was later proven incorrect?
Atoms are indivisible (indestructible). It was proven that they were composed of smaller
c. Explain or illustrate his model of the atom.
An atom with no internal particles.
2. a. What did J. J. Thomson contribute to the atomic model?
J. J. Thomson discovered the electron with his Cathode Ray Tube experiment.
b. Explain or illustrate his Plum Pudding Model of the atom.
After Thomson discovered the electron, he developed an atomic model called the Plum
Pudding model. ( chocolate chip cookie model). Since most matter does not shock us, he
concluded that atoms consists of an equal distribution of protons (+) and electrons (-). This
makes most matter composed of neutral atoms.
3. a. What did Ernest Rutherford contribute to the atomic model?
He concluded that most of the atom is empty space, but there was a small dense region in the
atom composed of protons. He called this dense region the nucleus.
b. What was his experiment called?
Gold Foil Experiment (in text book, Chapter 4)
c. Illustrate Rutherford’s model of the atom.
He concluded that most of the atom is empty space, but there was a small dense region in the
atom composed of protons. He called this dense region the nucleus.
d. What was a problem with Rutherford’s model of the atom?
If the nucleus was very tiny and consisted of similar charged particles, protons, then they
believed the repulsion force would tear the nucleus apart. What kept this from
happening? They proposed there must be another particle in the nucleus minimizing this
repulsion force. James Chadwick later through scientific research confirmed this other
particle in the nucleus was neutrons.
4. a.What did Bohr contribute to the atom? Energy levels in which electrons are most likely
found in the electron cloud.
b. Illustrate Bohr’s model of the atom. Draw an example of Bohr’s model or look at your time
5. a. What did Schrodinger contribute to the current atom? That electrons can move to different
energy levels and they do not all move in circular orbitals, can move in other shapes.
b. Illustrate Schrodinger’s current model of the atom? Use your atomic model timeline to help you.
6. Which two subatomic particles contribute charge? Protons (+) and electrons (-)
7. a. Which two subatomic particles contribute mass? Protons (+) and neutrons (-)
b. Do these subatomic particles contribute mass equally?
Yes, if look at table in your notes on subatomic particles you will conclude that the mass of these
particles have equal contribution to the mass of the atom.
8. What is an atom’s atomic number? Very important for an atom!
a. Represent the number of atoms for that element.
b. Atom’s I.DL.
c. All atoms of the same element have the same number of protons.
d. It distinguishes one atom from another atom.
9. How many protons does gold (Au) have? 79 protons
10. What would happen if gold (Au) lost a proton? It would become Pt (platinum)
gold (Au)gained a proton It would become Hg (mercury)
11. What is an atom’s mass number?
 Mass of an individual atom or isotope
 Sum of protons and neutrons
 Unit of measurement most common is amu.
12. a. Complete the table below these neutral atoms.
# of protons
# of neutrons
# of electrons
b. According to the table, rank the elements in decreasing atomic number.
greatest to least: Zn, Mn, Fe, and Ca.
c. According to the table, rank the elements in increasing mass number.
Lightest to heaviest: Ca, Fe, Mn, Zn
d. According to the table, which element has the most number of electrons.
13. What is an isotope
Atoms of the same element that have different number of neutrons. This also means the
different isotopes of an element have different mass numbers.
14. Iodine has three isotopes.
I-127 with a natural abundance of 80%.
I-126 with a natural abundance of 17%.
I-128 with a natural abundance of 3 %
a. Complete the table on these neutral isotopes of Iodine.
Iodine Isotopes
# of protons
# of neutrons
# of electrons
a. Why do Iodine’s isotopes have the same atomic number but different mass numbers?
Their atomic numbers (# of p+) are the same because they are isotopes of the same
element. They have different mass numbers because their number of neutrons vary from
one isotope to another; we know that neutrons affect the mass number of an isotope.
b. Calculate the atomic mass for Iodine.
 To do this one needs the Iodine’s isotopes mass numbers and natural abundance
I- 127:
I- 126:
127 x .80 = 101.6 amu (how much I-127 contributes to the average mass of I)
126 x .17 = 21.42 amu (how much I-126 contributes to the average mass of I)
128 x 0.03 = 3.84 amu (how much I-128 contributes to the average mass of I)
126.86 or with sig. figs: 126.9 amu
( Keep in mind that I will not count off for sig. figs on this test.  )
c. What unit is used to express the atomic mass for elements? Why did scientists’ select this
unit of measurement over the metric system? Amu values are easier to use than grams
(scientific notation!) when calculating mass numbers and atomic mass.
d. What is the difference between Iodine’s mass numbers and Iodine’s atomic mass?
Mass number: isotopes mass Atomic Mass: Average mass of Iodine taking into
consideration ALL the isotopes of Iodine.
e. Which iodine’s isotope occurs most common in nature? I-127
15. Illustrate the atomic models for
Li-9 using Bohr’s Model.
Li-7: p+ = 3 e-= 3 no= 4
Li- 9 p+ = 3 e- = 3 no = 6
Now illustrate where these sub-particles are located in the atom. Which ones are in nucleus and
which ones are in the vase empty space around the nucleus called the electron cloud.
16. a. Identify the two types of forces within an atom. Nuclear Forces within the nucleus
between protons and nucleus. Electrostatic forces between charged particles.
b. Give an example of each type of force within the atom.
Nuclear force between protons and neutrons.
Electrostatic force: attractive force between protons and electrons; repulsion force
between protons and protons in the nucleus or repulsion force between electrons and
electrons in the nucleus.
c. Which force is weaker: Electrostatic forces because the attractive force between the
protons and electrons is not enough to pull the protons from the nucleus. Nuclear force is
stronger than electrostatic force.