Chemistry Notes (pg. # 1)
Chemistry _ _
- Def: The study of all ______and the ______they
can undergo.
-The study of m______and e______
The word “Chemistry” comes from the word “Alchemy”, and has its roots in this “endeavor”.
Chemistry, the C______science:
-Chemistry has been called the c______science because
it o______so many other sciences.
Ex. Biology, physics, engineering, medicine
-Chemistry is considered the central science, and the idea of the ______is central to the central science.
Atomic Theory:
Question: What would happen if you were able to cut a piece of aluminum foil over and over and over…Would you always still have aluminum?
Democritus- G______p______(450 B.C.) who proposed the idea of atoms. He called them “______”
-Democritus believed that atomos were small, i______particles.
______- The search for a general understanding of reality by chiefly speculative rather than observational means.
-Limitation of ______: Does not use ex______.
______- systematic knowledge of the physical or material world gained through observation and e______.
-Limitation of ______: Limited to information gained through p______e______.
-The ideas of Democritus were dismissed by his fellow philosophers through the use of l______; however, the idea of the atom was re-visited by the s______John Dalton in the early 1800’s.
Modern View of The Atom:
The atom is composed of ______, ______, and ______.
Particle: Mass: Charge: Location:
1.0073 amu (+)
1.0087 amu
0.0006 amu
Question: How did scientists determine that the atom is made up of ______, ______, and ______?
-Also, how did they determine that there is a ______and an electron “______”?
Evidence for the Negative Electron:
Cathode Ray T_____ Experiment:
The Cathode Ray T______experiment showed that by deflecting a stream of particles with a magnet, atoms must contain n______c______p______.
-This was significant because it showed that atoms were not simply small indivisible “balls”, but rather had a s______.
-From the Cathode Ray Tube Experiment came the P____ P_____ model of the Atom.
(pg. # 1 continued…)
Evidence For the Positive Nucleus:
Rutherford’s G______F______experiment:
Rutherford shot (+) particles at a sheet of gold foil.
Results: Most of the particles went ______.
Some particles deflected s______b______
Analysis: 1.)This showed that most of the atom is in fact
e______s_____
2.)Also, the positive charge is very c______in a
small ______.
3.) This experiment disproved the ______
______.
Chemistry Ch. 3 Notes (pg. # 2)
Question:What makes one element different from another?
Ex. Why is copper different than aluminum?
Hint: It probably has something to do with the ______.
Henry Moseley- English scientist who determined what made atoms of the various elements unique from each other. He found that each element has a unique p______c______in the nucleus, and thus a certain n______of ______.
Atomic Number:
- Atomic Number- The number of p______in the nucleus.
Elements are identified by their A______N______.
Ex. Indicate which element has each of the following atomic numbers:
- 34 ______
- 12 ______
- 7 ______
- 6 ______
Ions:
- A neutral atom has an e______number of protons and e______.
Ex. A neutral Li atom has ___protons and
____ electrons
-An _____ is an atom (or small molecule) that has either ______or______an electron or electrons.
-Ions as a result have a net c______
Ex. Na (neutral) has ___ protons and ___ electrons
Na+ has ____ protons and ____ electrons
Ex. Determine how many protons and electrons each of the following ions have.
Ca2+ Al3+
F- N3-
Isotopes:
Isotope- Atoms of the s______element with a different number of ______.
Ex. Carbon-12 isotope:
____ protons, ____ neutrons
Carbon-14 isotope:
____ protons, ____ neutrons
Mass Number: The mass number of an isotope is the number of ______plus the number of ______.
Ex. Carbon-12
Ex. How many protons and neutrons does an Oxygen-15 atom have?
Protons = ______Neutrons = ______
Notation of Isotopes:
Ex. 37Cl
Ex. How many protons and neutrons do the following isotopes of carbon have?
12C 13C 14C
Chemistry Ch. 3 Notes (pg. # 3)
The Atomic Mass Unit:
1 a.m.u. is defined to be _____ the mass of a ______isotope.
- In other words, a ______isotope has a mass of exactly ______a.m.u.
Average Atomic Mass and Relative Abundances of Isotopes:
- All isotopes of an element do not have the same ______.
- The Average Atomic Mass is a w______average of all
the isotopes of an element
-The average atomic mass appears on the ______
______of the ______.
6
C
12.011
- Certain Isotopes of an element are more s______than others. As a result, there is a Relative Abundance of each isotope.
Relative Abundance- The percentage of an element that is composed of a certain isotope.
ex. The relative abundance of 12C in carbon is 98.89%.
- So, in any sample of carbon, 98.89% of the
sample will be the carbon-12 isotope.
(note: Notice how the average atomic mass of
carbon is very close to 12 amu)
Calculating Average Atomic Mass:
Avg. Atomic Mass = (Mass of Isotope 1)(% abundance/100) +
(Mass of Isotope 2)(% abundance/100) +…
Ex. Strontium has four isotopes with the following masses:
83.913 amu (0.56%)
85.909 amu (9.86%)
86.909 amu (7.00%)
87.906 amu (82.58%)
Calculate the average atomic mass of strontium.