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Chemical Foundations: Elements, Atoms and Ions – Chapter 4
Elements
All matter consists of about 100 elements.
An element is a fundamental chemical substance.
The smallest particle of an element is an ____________..
Elements cannot be broken down by chemical means to a
simpler substance.
Distribution of Elements
Chemical elements are not distributed equally in nature.
_________________ is the most abundant element in the universe.
_________________ is the most abundant element on earth and in the human body.
Names of the Elements
Names for the chemical elements come from a variety of sources, including Latin, location of
discovery, and famous scientists.
Symbols have one or two letters, with the first letter always capitalized and the second letter is
lower-case when necessary.
Introduction to the Periodic Table
The periodic table was designed by ____________________and currently arranges the elements
according to their atomic numbers and in groups by their chemical properties
(_________________).
Elements can be classified as __________________________________.
Elements can also be classified by special _________________ with similar chemical properties.
Such groups include:
____________________________________________________________________.
Elements can be classified as __________________________________:
Most elements are _________________.
Metals have the following properties:



Nonmetals have the following properties:


Elements in Their Nature States
Most elements are found in nature combined with other elements.
Elements that are found in uncombined form in nature include gold, silver, copper, and platinum
as well as the noble gases (He, Ne, Ar, Kr, Xe, Rn).
Elements That Exist as Diatomic Molecules
Diatomic molecules contain exactly ____________________________.
Seven elements exist as diatomic molecules – __________________________________.
Allotropes
Some elements exist in different forms but in the same state of matter…they are allotropes.
Examples:
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Chemical Foundations: Elements, Atoms and Ions – Chapter 4
Compounds
A compound is
There
are two general types of compounds:
Molecular –
Ionic –
Cation –
Anion –
Chemical Formulas
A chemical formula
Characteristics
of chemical formulas:




A formula does not show the arrangements of atoms in a compound.
Examples:
Atoms
Early Models of the Atom.
The first known processes of chemical principles occurred in ____________________________.
In Greece, _________________ attempted to classify all matter as being derived from water,
which could solidify in earth or vaporize into air.
Thales successors further classified matter into four components:
_________________ became the most influential of all Greek philosophers.
He believed that nature had four qualities:
The four basic elements of nature possessed combinations of these qualities.
Because of this, he proposed that substance could be changed into other substance
because of shared qualities (ex. lead into gold = alchemy).
Aristotle’s ideas prevailed for nearly 2000 years!
One of the first recorded ideas about atoms was proposed by _________________, a teacher
who lived in Greece in the fourth century B.C.
He believed that all substances were made of ________________________________.
 His theories had no experimental foundation and were held with little regard.
His ideas were virtually lost because of Aristotle’s popular theories.
Modern theories of the atom largely developed based on the works of _____________________,
an English schoolteacher.
Dalton, unlike Democritus, used experiments to justify his theory.
Dalton’s Atomic Theory:




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Chemical Foundations: Elements, Atoms and Ions – Chapter 4
Composition of Compounds
The law of definite composition
– In water, the mass ratio is ALWAYS 11.2% H and 88.8 % O. If the ratio of H to O
does not equal this, then the compound in not water, but some other hydrogen – oxygen
compound.
Example
Composition of Compounds
The law of multiple proportions
Example
Just
– Water = 11.2% H to 88.8% O; Hydrogen Peroxide = 5.9% H to 94.1% O.
How Small Is an Atom?
An atom is the smallest particle of an element that retains the properties of that element.
Atoms are extremely small and only the surface of atoms can be viewed with the use of
a scanning tunneling microscope.
If 100,000,000 copper atoms were placed side-by-side in a straight line, they
would measure 1 cm in length.
One copper penny contains 2.4 x 10 22 atoms, about 4 trillion times greater than
Earth’s human population!
Structure of the Nuclear Atom
Electrons.
Contrary to Dalton’s theory, atoms are divisible.
The first subatomic particle to be discovered was the _________________, a
negatively charged subatomic particle, in 1897 by _________________________.
Thomson passed an electrical current through a contained gas. The result was the
formation of a _________________, a beam that traveled from one metal plate
(electrode) to another metal plate (electrode).
The plate where the negatively charged beam originated is called the
_________________; the beam travels to the positive plate called the
_________________.
The beam was always attracted to a defined positive plate and repelled by a
defined negative plate.
Like charges _______________ and opposites _______________.
The beam must be comprised of negative particles, which Thomson
called electrons.
Through additional experimentation, Thomson determined the mass of an
electron to be __________________________________.
He actually determined the _________________________________
of the electron.
Cathode ray tube diagram:
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Chemical Foundations: Elements, Atoms and Ions – Chapter 4
Structure of the Nuclear Atom
__________________________________,through his “oil-drop” experiment, was also able to
determine the charge-to-mass ratio. In addition, he measured the ________________________.
An electron carries exactly one unit of negative charge, and its mass is 1/1840 the mass
of a hydrogen atom (reported in 1916).
Protons and Neutrons.
Assumption for
the existence of positive charges.
are electrically neutral having _________________.
Electric charges are carried by particles of matter.
Electric charges always exist in _______________________of a single base
unit (no fractions of charges).
When a given number of negatively charged particles combine with an equal
number of positively charged particles, an _____________________is formed.
Atoms
Evidence
of the proton.
1886, _________________ observed a cathode-ray and found rays traveling
in the direction opposite to that of the cathode rays.
Goldstein called these rays _________________ and determined that they were
composed of positive charges.
These positively charged subatomic particles are called _________________.
A proton has a mass of 1840 times greater than that of an electron.
In
The neutron.
In 1932, ____________________(some also credit Irene Joliot Curie as well)
confirmed the existence of another subatomic particle that was neutral in charge.
The particle was named the _________________.
A neutron is also 1840 time more massive than the electron.
The
Atomic Nucleus.
Thomson proposed the ___________________________model of the atom based on his
discoveries.
Diagram:
In
1911, __________________________________ decided to test this accepted model
of the atom with his now infamous “gold-foil” experiment.
Rutherford, with a radioactive source, shot positively charged “alpha” particles
at a piece of gold foil that was surrounded by an extremely sensitive fluorescent
screen capable of detecting the path of the alpha particles as they passed through
the foil.
Rutherford expected all of the particles to easily pass through the foil with only
slight deflections as the positive particle came into contact with the positive
mass.
To everyone’s surprise, __________________________________!
Some of the particles were __________________________...also surprising.
The most profound discover was that approximately 1 in every 20,000 alpha
particle was deflected _________________!
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Chemical Foundations: Elements, Atoms and Ions – Chapter 4
Conclusions:




Diagram:
Distinguishing Between Atoms
Atomic Number
Elements are inherently different because they contain different numbers of protons in
the nucleus.
The atomic number (Z) of an element is
In
a neutral atom, the number of protons in the nucleus ____________ the number of
electron outside of the nucleus.
Mass Number.
The mass number (A) refers to
Number

of neutrons = mass number - atomic number
N
= A
Z
Problem:
Determine the number of protons, neutrons, electrons, or the element refered
to by the following information.
Isotopes.
Also
contrary to Dalton’s theory, atoms of the same element are not necessarily similar
in all properties.
Most elements exist in more than one form based on the number of neutrons in the
nucleus of the atom.
Isotopes are atoms that
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Chemical Foundations: Elements, Atoms and Ions – Chapter 4
Because
the isotopes of an element have the same numbers of protons and electrons,
they are _________________. However, their nuclei are different, creating differences in
_________________.
Notations for writing isotopes.
Elemental Name-A.
Examples:
A

Z
X
Examples:
Problems
Determine
the number of each subatomic particle in the following:
14
40
19
99
6C
19K
9F
42Mo
Determine
the number of each subatomic particle in the following:
Beryllium-9
Nitrogen-14
Americium-241
Iodine-131
Atomic Mass
Actual masses of subatomic particle and atoms in general are small and impractical to use.
Scientists chose the carbon-12 isotope to be the foundation for a new, more effective and
efficient way of manipulating atomic masses.
An atomic mass unit (amu) is defined as one-twelfth the mass of a carbon-12 isotope.
All other isotopic masses are determined relative to this isotope and are written in “amu’s.”
In nature, most elements occur as a mixture of two or more isotopes.
Each isotope of an element has a fixed mass and a natural percent abundance.
The atomic mass of an element is a weighted average of the atoms in a naturally occurring
sample of an element. It is a “weighted average.” These values appear on the periodic table.
To determine the atomic mass, three values must be known.
The number of stable isotope of the element.
The mass of each isotope.
The natural percent abundance of each isotope.
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Chemical Foundations: Elements, Atoms and Ions – Chapter 4
Problems.
Chlorine
has two isotopes, chlorine-35 (atomic mass = 34.97 amu, relative abundance =
75.77%) and chlorine-37 (atomic mass = 36.97 amu, relative abundance = 24.23%).
Calculate the atomic mass of chlorine.
The
element copper has naturally occurring isotopes with mass numbers of 63 and 65.
The relative abundance and atomic masses are 69.2% for mass = 62.93 amu, and 30.8%
for mass = 64.93 amu. Calculate the average atomic mass of copper.
The Periodic Table: Organizing the Elements
Development of the Periodic Table.
o Although others developed a similar arrangement of the elements, Dmitri Mendeleev (18341907) is given credit for creating the first systematic periodic table.
o His periodic table was arranged the elements according to _________________.
o Mendeleev thought that these periodic properties were correlated with an
__________________________________.
o Although some flaws existed in his table, he assumed that his assumptions were correct.
In
1913, ___________________________, determined that periodic properties are correlated with an
__________________________________.
This is how our periodic table is arranged today.
The
Modern Periodic Table.
The periodic table is considered one of the most revolutionary scientific documents every
created. Possessing the ability to both understand and use is unlocks many of the underlying
concepts of chemical and subatomic activity.
Regions of the periodic table.
Periods are
There are 7 periods.
Properties of the elements _________________ a period.
Groups are vertical columns of elements.
There are 18 major groups.
Properties of the elements __________________________________.
The periodic law states that
The Periodic Table: Organizing the Elements - Refer to Blank Periodic Table.
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Chemical Foundations: Elements, Atoms and Ions – Chapter 4
Metals
Physical propertiesAll except Hg are _________________ at room temperature
Chemical propertiesWhen this compound rubs off the surface of the elemental metal it is called ________________.
Metals give up e- to get to a __________________________________.
Hydrogen
Hydrogen fits into its own group and is not an alkali metal or even a metal.
This is because it is only 1 proton and 1 electron (no neutrons).
Although under the extreme pressure on Jupiter it may act like a metal.
Nonmetals
Physical propertiesCan be solid, liquid or gas at room temperature depending on the element.
Nonmetals take e- to get a __________________________________.
Metalloids (semiconductors)
Can be shiny or dull, conduct fairly well, and are ductile and malleable or brittle.
These elements have become really important because of the computer revolution.
Computer chips are made out of semiconductors _________________.
By position Al is a metalloid, but its properties make it a light metal
The Nature of Electric Charge
The properties of electric charge:
Charges are one of two types:
Unlike charges attract and like charges repel.
Charge is transferred from one object to another by contact or by induction.
The force of attraction is expressed by:
Discovery of Ions
________________________________ discovered electrically charged ions.
________________________________ explained that conductivity results from the dissociation
of compounds into ions:
Cation – positive charge – __________________________________.
Anion – negative charge – __________________________________.
What causes reactivity of elements?
All atoms react to have a completely __________________________________.
For the moment we will only concentrate on main group elements
Noble gases have _________________.
Elements that are really close to an octet (halogens and alkali) tend to be the most reactive.
Gaining electrons
Metals lose electrons, nonmetals gain electrons and metalloids can go either way is a loose rule.
Obviously the quickest way for something that has more than 4 electrons to get to 8 is to gain
electrons (through chemical bonds).
Halogens _________________, oxygen’s group _________________, nitrogen’s group
_________________.
Losing Electrons
Metals will gain a full valence shell by losing electrons to obtain an octet beneath it.
Alkali metals will _________________; alkaline earth metals will _________________, etc.
Transition metals often lose electrons in varying amounts and predictability is difficult.
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