•Elements and the Periodic
Table
• Classification is arranging items into groups
or categories according to some criteria.
• The act of classifying creates a pattern that
helps you recognize and understand the
behavior of fish, chemicals, or any matter in
your surroundings.
• These fish, for
example, are
classified as
salmon because
they live in the
northern Pacific
Ocean, have
pinkish colored
flesh, and
characteristically
swim from salt to
fresh water to
spawn.
• Classifying Matter
• Matter is usually defined as anything that has mass
and occupies space.
• Metals and Nonmetals
– A metal had the following properties.
•
•
•
•
Metallic luster
High heat and electrical conductivity.
Malleability, able to be rolled or pounded into a thin sheet.
Ductile, can be pulled into a wire.
– A nonmetal has the following properties
• No metallic luster
• Poor conductor of heat and electricity.
• When it is a solid it is brittle so it cannot be pounded
or pulled into a wire.
• Most matter can be classified
as metals or nonmetals
according to physical
properties. Aluminum, for
example, is a lightweight kind
of matter that can be melted
and rolled into a thin sheet or
pulled into a wire. Here you
see aluminum pop cans that
have been compressed
into1,600 lb bales for
recycling, destined to again be
formed into new pop cans,
aluminum foil, or perhaps
aluminum wire.
• Solids, Liquids, and Gases
– Gases have no defined shape or defined volume
• Low density
– Liquids flow and can be poured from one container to
another
• Indefinite shape and takes on the shape of the container.
– Solids have a definite volume
• Have a definite shape.
• (A)A gas dispenses throughout a container, taking the shape
and volume of the container. (B) A liquid takes the shape of
the container but retains its own volume. (C) A solid retains
its own shape and volume.
• Mixtures and Pure Substances
– A mixture has unlike parts and a composition that varies
from sample to sample
– A heterogeneous mixture has physically distinct parts
with different properties.
– A homogeneous mixture is the same throughout the
sample
– Pure substances are substances with a fixed composition
• A classification scheme for matter.
– A physical change is a change that does not alter the
identity of the matter.
– A chemical change is a change that does alter the
identity of the matter.
– A compound is a pure substance that can be decomposed
by a chemical change into simpler substances with a
fixed mass ratio
– An element is a pure substance which cannot be broken
down into anything simpler by either physical or
chemical means.
• Sugar (A) is a compound that can be easily
decomposed to simpler substances by heating. (B)
One of the simpler substances is the black element
carbon, which cannot be further decomposed by
chemical or physical means.
• Elements
• Reconsidering the Fire Element
– The phlogiston theory viewed phlogiston as a
component of all matter.
– The burning of a material was considered to be the
escaping of phlogiston from the matter.
– If a material did not burn, it was considered to contain no
phlogiston.
• The phlogiston theory.
(A) In this theory,
burning was considered
to be the escape of
phlogiston into the air.
(B) Smelting combined
phlogiston-poor ore with
phlogiston from a fire to
make a metal. (C) Metal
rusting was considered to
be the slow escape of
phlogiston from a metal
into the air.
• Discovery of Modern Elements
– Antoine Lavoisier suggested that burning was actually a
chemical combination with oxygen.
– Lavoisier realized that there needed to be a new concept
of elements, compounds, and chemical change.
– We now know that there are 89 naturally-occurring
elements and at least 23 short-lived and artificially
prepared.
• Priestley produced a gas (oxygen) by using sunlight to heat
mercuric oxide kept in a closed container. The oxygen
forced some of the mercury out of the jar as it was
produced, increasing the volume about five times.
• Lavoisier heated a measured amount of mercury to
form the red oxide of mercury. He measured the
amount of oxygen removed from the jar and the
amount of red oxide formed. When the reaction was
reversed, he found the original amounts of mercury
and oxygen.
• The number of known elements increased as new
chemical and analytical techniques were developed.
• Names of Elements
– The first 103 elements have internationally accepted
names, which are derived from:
• The compound or substance in which the element was
discovered
• An unusual or identifying property of the element
• Places, cities, and countries
• Famous scientists
• Greek mythology
• Astronomical objects.
• Here are some of the symbols Dalton used for atoms
of elements and molecules of compounds. He
probably used a circle for each because, like the
ancient Greeks, he thought of atoms as tiny, round
hard spheres.
• The elements of aluminum, Iron, Oxygen, and Silicon make
up about 88 percent of the earth's solid surface. Water on the
surface and in the air as clouds and fog is made up of
hydrogen and oxygen. The air is 99 percent nitrogen and
oxygen. Hydrogen, oxygen, and carbon make up 97 percent
of a person. Thus almost everything you see in this picture
us made up of just six elements.
– Chemical Symbols
• There are about a dozen common elements that have s
single capitalized letter for their symbol
• The rest, that have permanent names have two letters.
– the first is capitalized and the second is lower case.
• Some elements have symbols from their Latin names.
• Ten of the elements have symbols from their Latin or
German names.
– Symbols and Atomic Structure
• A molecule is a particle that is composed of two or
more atoms held together by a chemical bond.
• Isotopes are atoms of an element with identical
chemical properties, but different masses due to a
difference in the number of neutrons.
• The atomic mass of an element is the average of all
the atomic masses of the isotopes.
– an isotopes contribution is determined by its
relative abundance.
• Using information from the fixed mass ratios of
combining elements, Dalton was able to calculate
the relative atomic masses of some of the elements.
Many of his findings were wrong, as you can see
from this sample of his table.
• The mass of an element is the mass of the element
compared to an isotope of carbon Carbon 12.
– Carbon 12 is assigned an atomic mass of 12.00 g.
– 12.00 is one atomic mass unit
• The number of protons and neutrons in an atom is its
mass number.
• Atomic numbers are whole numbers
• Mass numbers are whole numbers
• The atomic mass is not a whole number.
• A schematic of a mass spectrometer. The atoms of a sample
of gas become positive ions after being bombarded by a
beam of electrons. The ions are deflected into a curved path
by a magnetic field, which separates them according to their
charged-to-mass ratio. Less massive ions are deflected the
most, so the device identifies different groups of particles
with different masses.
• A mass spectrum of chlorine from a mass
spectrometer. Note that that two separate masses of
chlorine atoms are present, and their abundance can
be measured from the signal intensity. The greater
the signal intensity, the more abundant the isotope.
• The Periodic Law
• Dmitri Medeleev gave us a functional scheme with
which to classify elements.
– Mendeleev’s scheme was based on chemical properties of
the elements.
– It was noticed that the chemical properties of elements
increased in a periodic manner.
– The periodicity of the elements was demonstrated by
Medeleev when he used the table to predict to occurrence
and chemical properties of elements which had not yet
been discovered.
• Mendeleev left blank
spaces in his table when
the properties of the
elements above and
below did not seem to
match. The existence of
unknown elements was
predicted by Mendeleev
on the basis of the blank
spaces. When the
unknown elements were
discovered, it was found
that Mendeleev had
closely predicted the
properties of the elements
as well as their discovery.
• The Periodic Law
– Similar physical and chemical properties recur
periodically when the elements are listed in order of
increasing atomic number.
• The Modern Periodic Table
• Introduction
– The periodic table is made up of rows of elements and
columns.
– An element is identified by its chemical symbol.
– The number above the symbol is the atomic number
– The number below the symbol is the rounded atomic
weight of the element.
– A row is called a period
– A column is called a family
• (A) Periods of the periodic table, and (B) families of
the periodic table.
• Periodic Patterns
– The chemical behavior of elements is determined by its
electron configuration
– Energy levels are quantized so roughly correspond to
layers of electrons around the nucleus.
– A shell is all the electrons with the same value of n.
• n is a row in the periodic table.
– Each period begins with a new outer electron shell
– Each period ends with a completely filled outer shell that
has the maximum number of electrons for that shell.
– The number identifying the A families identifies the
number of electrons in the outer shell, except helium
– The outer shell electrons are responsible for chemical
reactions.
– Group A elements are called representative elements
– Group B elements are called transition elements.
• Chemical Families
– IA are called alkali metals because the react with water
to from an alkaline solution
– Group IIA are called the alkali earth metals because
they are reactive, but not as reactive as Group IA.
• They are also soft metals like Earth.
– Group VIIA are the halogens
• These need only one electron to fill their outer shell
• They are very reactive.
– Group VIIIA are the noble gases as they have completely
filled outer shells
• They are almost non reactive.
• Four chemical families of the
periodic table: the alkali metals
(IA), the alkaline earth metals
(IIA), halogens (VII), and the
noble gases (VIIIA).
• Metals, Nonmetals, and Semiconductors
– Chemical behavior is determined by the outer electrons.
• These are called valence electrons
– These outer shell electrons are represented using electron
dot diagrams.
– The noble gases have completely filled outer shells and
are therefore stable.
• All other elements react so as to fill their outer shell and
become more stable.
• Electron dot notation for the representative
elements.
– When an atom or molecule gain or loses an electron it
becomes an ion.
• A cation has lost an electron and therefore has a
positive charge
• An anion has gained an electron and therefore has a
negative charge.
– Elements with 1, 2, or 3 electrons in their outer shell tend
to lose electrons to fill their outer shell and become
cations.
• These are the metals which always tend to lose electrons.
– Elements with 5 to 7 electrons in their outer shell tend to
gain electrons to fill their outer shell and become anions.
• These are the nonmetals which always tend to gain electrons.
– Semiconductors (metalloids) occur at the dividing line
between metals and nonmetals.
• The location of metals, nonmetals, and
semiconductors in the periodic table.
• (A) Metals lose their outer electrons to acquire a
noble gas structure and become positive ions. (B)
Nonmetals gain electrons to acquire an outer noble
gas structure and become negative ions.
• The periodic table of the elements.