Download Chemistry Honors Unit 2 Study Guide Atomic Theory Mr. Brown Use

Chemistry Honors Unit 2 Study Guide
Atomic Theory
Mr. Brown
Use this study guide as a “checklist” to study for the unit test. Check off items as you master them to gain a better
understanding of what you really need to focus your study time on. To do well on the test be prepared to:
____ 1. Know how to read, comprehend, and fill in missing information on an “atom/ion” chart. Be well versed on how
to determine the number of protons, neutrons, electrons for a neutral atom or ion. Determine the charge of the ion
(positive or negative and numerical value of the charge such as 2- or 3+)
____ 2. Differentiate between the terms: mass number, atomic number, and average atomic mass.
____ 3. Differentiate and recognize examples of the terms “ion” and “isotope”
____ 4. Calculate the average atomic mass of isotopes in a given problem and/or the relative abundance of an
isotope.
____ 5. Understand the significance to the history of the study of chemistry by the following scientists:
John Dalton- He explained the three laws stated above with his Atomic Theory.
1.
2.
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All matter is composed of small particles called atoms.
Atoms of the same element are all identical; atoms of different elements are different.
Atoms can’t be subdivided, created nor destroyed.
Atoms of different elements combine in simple whole number ratios to form compounds.
In a chemical reaction, atoms are combined, separated or rearranged.
Joseph John Thomson- He discovered the electron and established that they were a part of all atoms. He
measured the charge to mass ratio of the electron. He came up with the plum pudding model of the atom in which
the electrons were thought to be evenly distributed throughout the atom as raisins are throughout a pudding.
Robert Millikan- He measured the charge on an electron in his famous oil drop experiment. Also, using Thomson’s
charge to mass ratio, he then calculated the mass of the electron.
Ernest Rutherford- He set up an experiment in which alpha particles were shot at a piece of gold foil. He was
surprised to see that some of the particles were deflected back. He reasoned that the atom was made up of a very
small, dense, positively charged center and that the rest of the atom was mostly empty space, like our model of the
solar system where the sun is like the central nucleus.
Niels Bohr- Using the bright line emission spectrum of the excited hydrogen atom, he reasoned that the electrons
traveled outside the nucleus in orbits of specific energy values.
____ 6. Memorize the elemental symbol, atomic number, and element name for elements #1-40.
____ 7. Contrast between the terms “Law of Definite Proportions” and “Law of Multiple Proportions”.
Law of Definite Proportions/Composition = Chemical compounds always contain the same elements in exactly the
same proportions by mass regardless of the amount or source of the sample.
EX. NaCl always contain 39.34% by mass of Na and 60.66% by mass of Cl.
Law of Multiple Proportions = If two or more different compounds are formed from the same 2 elements, then the
ratio of the masses of the 2 nd element combined with a certain mass of the 1st element is always a ratio of small
whole numbers.
EX. CO and CO2 each contain C and O. The ratio of O:C in CO2 is 32:12 = 2.66. The ratio of the mass of O:C in
CO is 16:12 = 1.33. 2.66:1.33 = 2:1.
____ 8. Recognize that 1 proton and 1 neutron each mass at 1.00 amu and that the amu is recognized as 1/12 the
mass of a carbon-12 atom.
____ 9. Understand the relationship between the gram, amu, and how Avogadro ’s number was derived:
The Mole – The mole has several true definitions that follow:
= a measure of the amount of matter.
= a counting unit, like a dozen, that always represents
6.022 x 1023 particles
Ex. A mole of carbon contains 6.022 x 1023 atoms of carbon.
A mole of H2O contains 6.022 x 1023 molecules of H2O
= number of atoms (6.022 x 1023 atoms) necessary to make up amount of a substance equal to its atomic
mass in grams.
So the mole plays an important role in chemistry because it relates mass to the number of atoms or particles.
6.02 X 1023 is called Avogadro ’s number (NA) after the scientist that did this work.
____ 11. Memory Lane:
____ a) Identify and describe the three states of matter solid, liquid and gas. Understand which ones have an
indefinite/definite shape and volume.
____ b) Explain and provide examples of a chemical change and a physical change.
____ c)Explain and provide examples of physical properties and chemical properties.
____ d) Distinguish between elements and compounds and be able to list examples of each.
____ e) Memorize and apply the density equation: Density = Mass / Volume to solve for 1 of the 3 variables.