Dmitri Mendeleev studied the properties of
the 63 known elements in an attempt to
He used an element’s melting point, density,
color and atomic mass.
Atomic Mass – the average mass of all the
isotopes of that element.
Mendeleev noticed that a pattern of
properties appeared when he arranged the
elements in order of increasing atomic mass.
He found that the properties of the elements
Mendeleev called his arrangement of the
elements a periodic table because of the
repetition of properties.
He left blank spaces in his table and
predicted that these spaces would be fill by
elements that had not yet been discovered.
He was even able to predict the properties of
The modern periodic table is arranged
according to increasing atomic number.
Nucleus – center of the atom and contains
protons and neutrons.
Protons – positively charge particles in the
nucleus of the atom.
Every atom of the same element has the
same number of protons, which is called the
Neutrons – particles in the nucleus which
have no charge (neutral)
Protons and neutrons have about the same
atomic mass and make up most of the mass
of the atom.
Electrons – particles moving around in the
space around the nucleus which have a
Contains information for each of the known
Contains the atomic number, chemical
symbol, name and atomic mass for each
Chemical Symbol – abbreviation of an
element’s name. Its either one or two
letters. Ex. – Fl or C
The periodic table is made up of rows called
The periodic table is made up of columns
called groups or families.
There are 7 periods and 18 groups.
The properties of an element can be
predicted from its location in the periodic
Metals are shown on the left of the table
Nonmetals are shown on the right of the
Metalloids are located between the metals
The pattern is repeated in each period and
accounts for the fact that elements in the
same group have similar characteristics.
The majority of the elements in the periodic
table are metals.
They are good conductors of electric current
The metals begin on the left side of the table
and extend most of the way across.
The physical properties of metals include
luster, malleability, ductility and
A material that has a high luster is shiny and
A malleable material can be hammered or
rolled into flat sheets.
A ductile material can be drawn into long
Thermal conductivity is the ability of an
object to transfer heat.
The ability of an object to carry electric
current is electrical conductivity.
Reactivity – the ease and speed with which
an element reacts with other substances.
Metals usually react by losing electrons.
Corrosion – the deterioration of a metal due
to a chemical reaction in the environment.
Metals are classified as one of the following:
Alkaline earth metals
Metals in mixed groups
Most reactive metals in the periodic table
Never found uncombined in nature because
they are so reactive
Low melting points
Harder, denser and melt at higher
temperatures than the alkali metals
Highly reactive, but not as much as the alkali
Group 3 – 12
Most are hard and shiny solids with high
melting points and high densities
Less reactive than groups 1 and 2
Some of the elements in groups 13-16 are
Two rows of elements placed below the main
part of the table are the lanthanide and
Elements found after Uranium-92 are
synthetic elements (man-made)
A nonmetal is an element that lacks most of
the properties of a metal.
With the exception of hydrogen, nonmetals
are found on the right side of the table.
Most nonmetals are poor conductors of
electric current and heat.
Solid nonmetals tend to be dull and brittle.
Nonmetals usually have lower densities than
For chemical properties, nonmetals usually
gain or share electrons when they react with
There are nonmetals in group 1 and groups
The families containing nonmetals are the
In group 14, only carbon is a nonmetal
The nitrogen family has two, nitrogen and
The oxygen family has three, oxygen, sulfur and
The halogens in group 17 are fluorine, chlorine,
bromine and iodine. Halogens are very reactive
and fluorine is the most reactive.
The noble gases are in group 18. They are
Hydrogen is not grouped with any family because
its properties are so different.
Elements that have properties of metals and
some of nonmetals are called metalloids.
All metalloids are solid at room temperature,
and are brittle, hard and somewhat reactive.
Metalloids such as silicon, germanium and
arsenic are used to make semiconductors,
which are substances that can conduct
electric current under some conditions but
not under others.
The idea of the atom dates back to 430 B.C.
Today the atom is defined as the smallest
particle that can still be considered an
Atomic theory grew as a series of models
that developed from experimental evidence.
As more evidence was collected, the theory
and models were revised.
Dalton described the atom as the indivisible particle that
makes up an element. He identified other characteristics
of atoms, all of which remain part of the modern model.
Thomson’s discovery of negatively charged particles called
electrons disproved Dalton’s indvisible-atom idea. He
proposed a model in which electrons were scattered
throughout a ball of positive charge.
Rutherford proposed the existence of a nucleus, a small,
positively charged region of an atom containing positively
charged particles that he called protons.
Bohr revised the model to propose that electrons were
found only in specific orbits around the nucleus.
The modern cloud model suggests that an electron’s
movement is related to its energy level, and electrons
move rapidly within a cloudlike region around the nucleus.
At the center of the atom is a tiny, dense
nucleus containing protons and neutrons.
Surrounding the nucleus is a cloudlike region of
Almost all of the mass of an atom is
concentrated in the nucleus.
Protons have a charge of +1 and have a mass of 1
Neutrons have no charge and a mass of 1 amu.
Electrons have a negative charge and a mass of