Chapter 2: Atoms and Elements
Chapter 2 Problem Set
Pages 94-97
26, 28, 30, 32, 36, 42, 46, 48, 50
2.1
ORIGINS OF ATOMIC THEORY
What was Democritus’ concept of the atom?
John Dalton & His Atomic Theory
Dalton’s atomic theory postulates:
 All matter is made of atoms
 All atoms of a given element are identical
 Atoms combine in the ratio of small whole numbers
 A chemical reaction involves only combination, separation, or rearrangement of atoms
The Law of Conservation of Matter …
The Law of Constant Composition …
The Law of Multiple Proportions …
2.2
PROTONS, NEUTRONS, & ELECTRONS: A HISTORICAL PERSPECTIVE
ELECTRICITY
Radioactivity
Henri Becquerel discovered . . . . .
Marie Curie isolated . . . . . . . .
What are the three kinds of radiation?
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Electrons
What is electrolysis?
What is a fundamental “particle” of electricity?
What evidence is there that atoms are composed of smaller particles?
What are some properties of cathode rays?
Who determined the charge to mass ratio of a beam of cathode rays?
What was Millikan’s contribution which enables us to calculate the mass of an electron?
Protons
How were positive particles discovered?
Neutrons
How were neutrons discovered?
Why did it take so long to discover neutrons?
The Nucleus of the Atom
How did Rutherford discover the nucleus of the atom?
2.3
ATOMIC STRUCTURE
Atoms have no net charge so the number of electrons outside the nucleus equals the number of
protons in the nucleus
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2.4
ATOMIC NUMBER & THE MASS OF AN ATOM
What is an atomic number of an element?
One atomic mass unit , amu is 1/12 of the mass of an atom of …
relative atomic masses pg 71 good explanation
atomic number (Z)
mass number (A)
A - Z = # neutrons
A
Z
X
common notation
EXAMPLE 2L.1 Atomic Composition
How many neutrons are in an atom of gold with a mass number of 197?
EXERCISE 2L.1
The number of neutrons in a given nucleus determines the
a. number of electrons
d. number of protons
b. atomic number
e. number of allotropes
c. mass number
EXERCISE 2L.2
What is the mass number of a phosphorus atom with 16 neutrons? Such an atom has a mass of
30.9738 amu. What is its mass in grams?
2.5
ISOTOPES
Atoms with the same atomic number but different mass numbers are called …
What are the names of the isotopes of hydrogen?
EXAMPLE 2L.3 Isotopes
Copper has two naturally occurring isotopes, one with 34 neutrons, & the other with 36 neutrons.
What are the mass numbers and symbols of these isotopes?
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2.6
ATOMIC WEIGHT (ATOMIC MASS)
The atomic mass of an element is the weighted average of the masses of its constituent isotopes.
EXAMPLE 2L.4 Calculating Average Atomic Mass from Isotopic Abundances
Naturally occurring chromium consists of four isotopes. It is
4.31% Cr-50 of mass 49.946 amu, 83.76% Cr-52 of mass 51.94 amu, 9.55% Cr-53 of mass 52.941
amu, and 2.38% Cr-54 of mass 53.939 amu. Calculate the atomic mass of Cr.
2.7
THE PERIODIC TABLE
Features of the Periodic Table
What are groups?
What are the horizontal rows called?
What are the main group elements?
Where are the transition elements?
Where are the metals?
Where are the nonmetals
Where are the metalloids?
Name the metalloids.
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Historical Development of the Periodic Table
How did Mendeleev develop the Periodic Table?
What was the genius of Mendeleev?
What did Moseley discover?
2.8
THE ELEMENTS, THEIR CHEMISTRY, AND THE PERIODIC TABLE
Group 1A, H and The Alkali Metals: Li, Na, K, Rb, Cs, Fr
What are some characteristic properties of the alkali metals?
What is the characteristic formula of compounds of the alkali metals with oxygen?
Group 2A, The Alkaline Earth Metals: Be, Mg, Ca, Sr, Ba, Ra
What are some characteristic properties of the alkaline earth metals?
What is the general formula of the compounds formed with oxygen?
The Transition Elements
What are some of the important transition elements?
What are the lanthanides?
What are the actinides?
Group 3A, The Boron Family: B, Al, Ga, In, Tl
What is the most important metal in Group 3A?
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Group 4A, The Carbon Family: C, Si, Ge, Sn, Pb
What are allotropes?
What are the allotropes of carbon?
What are some important properties of diamonds?
How does silicon exist in nature?
Group 5A, The Nitrogen Family: N, P, As, Sb, Bi
What is meant by the phrase, fixing atmospheric nitrogen?
What are some important uses of phosphorus?
Group 6A, The Oxygen Family: O, S, Se, Te, Po
What is the most important compound of sulfur?
What is an allotrope of oxygen?
Who discovered polonium?
7A, Halogens: F, Cl, Br, I, At
What are some properties of the halogens?
8A, Noble gases: He, Ne, Ar, Kr, Xe, Rn
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