Chemistry 30
Unit 1 Chemistry 20 Review
1.
Fact File Timeline and More
A. Democritus (460 to 370 BC) -Atoms are impenetrable and have a density proportional to
their volume
B. Lavoisier (1743-1794) – Found the Law of Conservation of Mass
C. John Dalton (1766-1844) – Proposed the Atomic Theory in 1803
D. J.J.Thompson (1856 – 1940) – the first to discover the electron in 1895 and then the first
to split an atom in 1905
E. Ernst Rutherford (Aug. 30, 1871 to Oct. 19, 1937) – in 1910 showed that there must be
an inner structure in the atom, later named the nucleus
F. Robert Millikan (March 22, 1868 to Dec. 19, 1953) – Began working in 1909 to prove
the charge of electons
G. Niels Bohr (Oct. 7, 1885 to Nov. 18, 1962) – Using concepts from the Quantum Theory,
he presented a picture of atom
H. James Chadwick (Oct. 20, 1891 to July 24, 1974) – Discovered the neutron in 1932
I. Louis de Broglie (1892 to 1987) – In 1924 he introduced the wave particle duality theory
which united the energy of a wave with the movement of the particle which helped create
quantum mechanics
Assignment #4: Atomic Scientists
Bohr was the first to propose this idea of energy levels. Using the Internet, check up on the
history of his work and answer the following questions:
1. What problems with Rutherford's theory was Bohr trying to explain?
The first problem was that the atom was very unstable because electrons that continually change
direction, speed, etc. would constantly be using up their energy ending in them spiraling into the
nucleus. The second problem was that his model did not explain that in some gasses the
electrons emitted a light at certain discrete distances, not at random areas.
2. The work of several men was used as the basis for Bohr's theory. Describe the
contribution of the following men to Bohr's theory:
o Max Planck
Determined Planck’s constant which helped to measure the distribution of energy in the full
spectrum of radiation. This helped Bohr to explain how electrons absorbed or emitted energy.
o
John Palmer
3. The study of light is central to Bohr's theory. Define the following terms as they relate to
light:
o Wavelength - distance between successive peaks or troughs
o Frequency - number of complete wavelengths that pass a given point in 1 second
o Photons - the smallest increment of radiant energy
Emission spectrum – a spectrum containing radiation of only specific wavelengths
4. Explain how Bohr's theory explains the emission spectrums of elements like hydrogen
using the terms above in question #3
o
Typical light consists of radiation that is composed of several wavelengths. When these
wavelengths are split into their different components, an emission spectrum is formed.
Assignment 11 Chemical Families
Info taken from:
http://www.chemicalelements.com/groups/alkali.html
The alkali metals, found in group 1 of the periodic table (formerly known as group IA),
are very reactive metals that do not occur freely in nature. These metals have only one
electron in their outer shell. Therefore, they are ready to lose that one electron in ionic
bonding with other elements. As with all metals, the alkali metals are malleable, ductile,
and are good conductors of heat and electricity. The alkali metals are softer than most
other metals. Cesium and francium are the most reactive elements in this group. Alkali
metals can explode if they are exposed to water.
The Alkali Metals are:
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Lithium
Sodium
Potassium
Rubidium
Cesium
Francium
The alkaline earth elements are metallic elements found in the second group of the
periodic table. All alkaline earth elements have an oxidation number of +2, making them
very reactive. Because of their reactivity, the alkaline metals are not found free in
nature.
The Alkaline Earth Metals are:
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Beryllium
Magnesium
Calcium
Strontium
Barium
Radium
The halogens are five non-metallic elements found in group 17 of the periodic table. The
term "halogen" means "salt-former" and compounds containing halogens are called
"salts". All halogens have 7 electrons in their outer shells, giving them an oxidation
number of -1. The halogens exist, at room temperature, in all three states of matter:
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Solid- Iodine, Astatine
Liquid- Bromine
Gas- Fluorine, Chlorine
The Halogens are:
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Fluorine
Chlorine
Bromine
Iodine
Astatine
The Oxygen Family, also called the Chalcogens, consists of the elements found in Group 16 of
the periodic table and is considered part of the Main Group elements. It consists of the elements
oxygen, sulfur, selenium, tellurium and polonium. The group is named after its first member,
oxygen, however the individual elements very quite widely due to the changing metallic
properties as one descends down the group. They can be found in nature in both free and
combined states.
Properties and Periodic Trends
All elements of the Oxygen family have 6 electrons in their outermost shell, with a valence
electron configuration of ns2np4, which accounts for the similar chemical properties between the
elements. As one moves down the group, metallic character increases, with tellurium being a
metalloid and polonium a metal. Melting point, boiling point, density, atomic radius, and ionic
radius all increase going down the group. Ionization energy decreases going down the group. The
most common oxidation state is -2, however sulfur can also exist at a +4 and +6 state and +2, +4,
and +6 oxidation states are possible for Se, Te, and Po.
http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/Main_Group_E
lements/Group_16:_The_Oxygen_Family
Assignment #12: Types of Chemical Bonds
Using any or all of the following sources of information to answer the following questions.
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http://users.senet.com.au/~rowanb/chem/chembond.htm
http://www.okstate.edu/jgelder/bondpage3.html#cen
http://members.aol.com/profchm/bonding.htm

http://www.woodrow.org/teachers/chemistry/links/chem1/Chapter5.html
1. What are the three types of chemical bonds?
Ionic, Covalent and Metallic
2. Describe what happens to the atoms when each type of bond forms.
Ionic – large electronegative difference and the one or more valence electrons are moved to the
other atom
Covalent – valence electrons are shared between the atoms, can be polar if the sharing is not
equal
Metallic – valence electrons shared between two metallic atoms
3. What types of elements (metal or nonmetal) form each type of bond?
Metallic (metal)
4. What is a molecule?
A molecule is the smallest particle of a substance that retains its chemical properties and is made
up of at least two atoms
5. What types of bonds form molecular substances?
Covalent Bonds
6. List 4 properties of these types of substances?
Melting/Boiling Point, Solubility, Electrical Conductivity
7. What is the difference between polar and nonpolar covalent bonds?
Polar means that there is a charge because the electrons are not shared evenly within the bond, so
one end is + and one end appears to be -. Nonpolar means that the electrons are shared evenly.
8. How does this differences between the two types of covalent bonds affect the properties
of the molecules that contain these bonds ?
Polar molecules are dipole, a + end and a negative end.