Download Chapter 3: The Elements Eli and Ethan Objective: To learn about the

Chapter 3: The Elements
Eli and Ethan
Objective: To learn about the relative abundances of the elements and to learn the names of some of
the elements.
Background Information
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All the materials of the earth can be chemically broken down into about 100 different
elements.
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Nature often uses a realtively small number of fundamental units to assemble even
extremely complex materials.
■Example: A group of substances that serve the human body in almost uncountable
ways, are all made by linking together a few fundamental units to form huge
molecules.
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115 different elements are known, and 88 of those 115 elements occur naturally.
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Sometimes when people say element, they mean a single atom of that element. While we
might call this a microscopic form of the element, sometimes we use the term element, we
mean a sample of the element large enough to weigh on a balance.
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Many element names derive from Greek, Latin, or German words.
● Symbols for the Elements
● Objective: To learn the symbols of some elements.
Important Information
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Many people use abbreviations to simplify the written word
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Similarly, chemists have invented a set of abbreviations or element symbols for the
chemical elements.
● These symbols consist of the first letter or the first two letters of the elements name. The first
letter is always capitalized, and the second is not.
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Ex: Fluorine: F
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Oxygen: O
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Carbon: C
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Neon: Ne
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Silicon: Si
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However, there a fair amount of irregularities. These elements are based on the original Latin
names.
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Ex: Gold: Au
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Lead: Pb
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Sodium: Na
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Iron: Fe
● All of these elements can be found on the periodic table of elements, where the symbol and the
name of the element are found, as well as other facts.
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Including the atomic number and atomic mass.
Dalton’s Atomic Theory
Objective: To learn about Dalton’s theory of atoms and to understand and illustrate the law of constant
composition.
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As scientists of the eighteenth century studied the nature of materials, several things
became clear.
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Most natural materials are mixtures or pure substances.
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Pure substances are either elements or combinations of elements called compounds.
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A given compound always contains the same proportions of the elements.
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■ Ex: Water will always contain 8g of oxygen for every 1 g of hydrogen.
This principle is known as the law of constant composition, meaning that a given compound
always has the same composition, regardless of where it comes from.
Based off of these observations, John Dalton, an English scientist offered an explanation
for them known as Dalton’s Atomic Theory. Below are the five parts of the theory.
Elements are made up tiny particles called atoms.
All atoms of a given elements are identical.
The atoms of a given element are different from those of any element.
Atoms of one element can combine with atoms of other elements to form compounds. A
given compound always has the same relative number and types of atoms.
Atoms are indivisible in chemical processes. That is, atoms are not created or destroyed in
chemical reactions. A chemical reaction simply changes the way the atoms are grouped
together.
Because Dalton’s theory was not originally accepted, he had to correctly predict the
formation of multiple compounds between two elements.
Ex: When there is one atom of nitrogen and two atoms of oxygen it becomes NO2 or when
there is one atom of nitrogen and one atom of oxygen it is solely NO.
After Dalton correctly predicted this, his theory became widely accepted.
Formulas of Compounds
Objective: To learn how a formula describes a compound’s composition.
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A compound is a distinct substance that that is composed of the atoms of two or more
elements and always contains exactly the same relative mass of those elements.
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This simply means that a compound always contains the same relative number of atoms for
each oxygen atom.
● Ex: Water always contains two hydrogen atoms for each oxygen atoms.
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The types of atoms and the number of each type in each unit (molecule) of a given
compound are conveniently expressed by a chemical formula.
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In a chemical formula, the atom is indicated by the subscript, a number that appears to the
right of and below the symbol for the element.
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Ex: The formula for water, H2o, indicates that each molecule of water contain two atoms of
hydrogen and one atom of oxygen.
Rules for Writing Formulas
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Each atom is represented by its element symbol.
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The number of each type of atom is indicated by a subscript written to the right of the
element symbol.
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When only one atom of a given type is present, the subscript 1 is not written as it is just
understood.
The Structure of the Atom
Objective: To learn about internal parts of an atom and to understand Rutherford’s experiment to
characterize the atom’s structure.
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A physicist concluded that all types of atoms contain negative particles, which are now
referred to as electrons.
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This physicist also concluded that there must be positive particles to balance out these
negative particles. The positive particles are known as protons, giving the atom no overall
change.
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Another scientist , Lord Kelvin decided that the atom might be something like plum
pudding. (A pudding that has raisins randomly distributed throughout)
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He reasoned this because he thought the atom might be similar to a uniform pudding of
positive charge with enough negative charge electrons to counter balance the positive. Thus the
plum pudding model of the atom came to be.
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In early 1911 a physicist, Ernest Rutherford, changed the ideas about the atom drastically.
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Rutherford found that some of the alpha particles were deflected by something in the air.
He designed an experiment that involved directed alpha particles toward a thin metal foil.
Surroudnign the foil was a detector coated with a substance that produced tiny flashes
whenever it was hit by an alpha particle.
● Most of the alpha particles passed straight through the foil, some were deflected at large
angles. , and some were reflected backward.
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He knew that if the plum pudding was right, then the massive alpha particles would crash
through the thin foil like cannonballs on paper.
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He expected the alpha particles to travel through the foil experiencing, at most, very minor
deflections of their paths.
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He disproved the plum pudding model.
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Nuclear Atom- An atom with a dense center of positive charge (the nucleus) around which
tiny electrons moved in a space that was otherwise empty.
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He concluded that the nucleus must have a positive charge to balance the negative charge
of the electrons and that it must be small and dense. He said it contained protons. A proton
had the same magnitude/size as the electron but it was just negative.
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He also was able to show that most nuclei contained a neutral particle that they named
neutron. It is slightly more massive than the proton but has no change.
Introduction to the Modern Concept of Atomic Structure
Objective: To describe some important features of subatomic particles.
Introduction to the Modern Concept of Atomic Structure
Objective: To describe some important features of the subatomic particles.
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Particle
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Relative Mass *
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Relative Charge
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Electron
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1
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-1
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Proton
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1836
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1+
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Neutron
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1839
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None
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If all atoms are composed of these same compounds, why do we have different
chemical properties?
○ The answer lies in the number and arrangement of the electrons.
Isotopes
Objective: To learn about the terms isotope, atomic number, and mass number.
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Isotopes- Atoms with the same number of protons but different numbers of neutrons.
The number of protons in a nucleus is called the atom’s atomic number.
The sum of the number of neutrons and the number of protons in a given nucleus is
called the atom’s mass number.
○ Number of neutrons + Number of protons = Mass Number.
Each box of this table contains a number written over one or two letters.
○ The letters are symbolic for the elements.
The number shown above each symbol is the atomic number.
Under it is the atomic mass.
The number of protons is the same as its atomic number.
All the elements in the periodic table that show similar chemical behavior are listed
vertically, as a “family of elements”. The ones that are the same, are similar.
○ These types of elements are called groups.
They have specific names.
○ EX: Group 1 (Column 1) is called Alkali Metals
○ Group 2 is called Alkaline Earth Metals
○ Group 7 is called Halogens
○ Group 8 is called Noble Gases
○ A large amount of elements that spans many vertical columns consist of the
transition metals.
○ Most of the elements are metals. Metals have the following characteristics:
■Efficient Conduction of heat and Electricity.
■Malleability (they can be hammered into thin sheets)
■Ductility (They can be pulled into wires)
■A lustrous, shiny appearance.
The relatively small number of elements that appear in the upper right hand corner of the
periodic table. These are called nonmetals. They lack the characteristics metals and
appear to have much more variation then metals do.
The elements that lie close to the non metals are called metalloids or semimetals.
Examples include: Germanium, Silicon, Arsenic, Antimony, and Tellurium.
Natural States of the Elements
Objective: To learn the natures of common elements.
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Gold, silver, and platinum are members of a class of metals called noble metals because
they are relatively non-reactive. (Noble means a class set apart.)
Group 8 is called noble gasses because they do not combine readily with those of other
elements. Group 8 consists of helium, neon, argon, krypton, and xenon.
Air contains nitrogen gas and oxygen gas. When we examine these two gasses, we find
that they do not contain single atoms, similarly to argon. But instead, they contain
diatomic molecules.
○ Diatomic molecules are molecules that are made up of two atoms.
■Some more include, nitrogen, fluorine, chlorine, bromine, and iodine.
○ Different forms of a given element are called allotropes.
Ions
Objectives: To describe the formation of ions from their parent atoms, and learn to name them.
To predict which ion a given element forms by using the periodic table.
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We can produce a charged entility- called an ion. This is done by taking a neutral atom
and adding or removing one or more electrons.
A positive ion, called a cation is produced when one or more electrons are lost from a
neutral atom.
A negatively charged ion is called an anion. An atom that gains one extra electron forms
an anion with a 1- charge.
Many substances contain ions. In fact, whenever a compound forms between a metal
and a nonmetal, it can be expected to contain ions. We call these substances ionic
compounds.
Important to remember that a chemical compound must have a net charge of zero. This
means that if a compound contains ions, then there must be both positive and negative
ions present. And the number of cations and ions must be such that the net charge is
zero.
TEST:
VOCAB.
1) Define the law of constant composition?
2) Define Dalton’s Atomic Theory?
3) What is the difference between an atom and compound?
4) What is the difference between electron and proton?
5) What is a neutron?
6) What are isotopes?
7) What is the periodic table used for?
8) How is the periodic table organized?
9) What is the difference between a Cation and and Anion?
10) What is a metalloid?
11) What are the properties of a metal?
12) What is a non-metal?
13) Where do you find the mass number and the atomic number on the periodic table?
14) What is a halogen?
15) What is a noble gas?
16) What group number is Alkaline Earth metals?
17) What group number is Alkali Metals?
18) Where are the transition metals on the periodic table?
19) What is a group on the periodic table?
20) What is a nuclear atom.
CHAPTER PROBLEMS
21) Give the chemical symbol for neon
22) Give the chemical symbol for silver
23) Give the chemical symbol for iron
24) Name all the characteristics an element must have to be a metal.
25) T or F The mass number of a nucleus represents the number of protons in a nucleus?
26) What does K stand for?
27) What does S stand for?
28) What does U stand for?
29) What does Pb stand for?
30) What is Zinc’s symbol?
Answers
1) A given compound always has the same composition, regardless of where it comes
from.
2) Elements are made up tiny particles called atoms. All atoms of a given elements are
identical.The atoms of a given element are different from those of any element.
Atoms of one element can combine with atoms of other elements to form
compounds. A given compound always has the same relative number and types of
atoms. Atoms are indivisible in chemical processes. That is, atoms are not created
or destroyed in chemical reactions. A chemical reaction simply changes the way the
atoms are grouped together.
3) Elements are made up of atoms and, compounds are combinations of elements that
make up pure substances.
4) Electrons are negative charged particles that make up the atom, while the protons
are positively charged.
5) A neutron is a neutral particle that makes up the atoms.
6) An isotope is an atom with the same amount of protons but diff numbers of
neutrons.
7) The periodic table is used to find out abbreviations for elements, their charges, their
atomic masses, and their atomic numbers.
8) In groups/families.
9) Cation is a positive ion while the anion is the negative ion.
10) A metalloid has properties of a metal and a non-metal.
11) It has efficient conduction of heat and electricity, it has to have malleability,
ductility, and it has to be lustrous.
12) A non metal is not shiny and is the opposite of a metal, it doesn’t have these
characteristics.
13) Mass number is under the element abbreviation and the atomic number is in the
upper corner.
14) Group 7
15) Group 8
16) Group 2
17) Group 1
18) They span through many vertical columns.
19) A family, which is a vertical line on it that all of the elements in that line have
similar chemical properties.
20) An atom with a dense center of positive charge around which tiny electrons moved
in a space that was otherwise empty.
21) Ne
22) Ag
23) Fe
24) It has efficient conduction of heat and electricity, it has to have malleability,
ductility, and it has to be lustrous.
25) F
26) Potassium
27) Sulfur
28) Uranium
29) Lead
30) Zi
31)