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The Periodic Table
Lesson 2
The Elements of Matter
An Element is a pure substance that is made up of
only one kind of atom
It cannot be broken down into other substances by
ordinary laboratory methods
How do we identify the element?
Atoms of different elements have different numbers
of protons that correspond to their atomic number
Elements
Hydrogen is the most common element in the
universe
The sun, and other stars, are made up mainly of
hydrogen
Other elements are created through fusion in a star.
This process occurs when the extreme heat of a star
joins hydrogen nuclei together.
Everything on Earth is made up of hydrogen or
elements that were formed by the fusion in stars
States of Matter
Most elements in their pure form are solids at room
temperature
Some elements are gases at room temperature… can
we name some of them?
Nitrogen, oxygen, hydrogen, neon, etc.
Only two elements are liquid at room temperature...
Can anyone guess what they are?!?
Bromine and Mercury
Even though Mercury is a liquid at room temperature,
it is still a metal!
Metals
A metal is an element that conducts heat and
electricity well
Most of the known elements, about ¾ or 75%, are
metals
They are shiny, and most have a gray or silver color
Examples are iron, lead and silver
Some exceptions are Gold and Copper
Malleability is another property of metals
Malleability means that metals can be bent and rolled
into sheets
Nonmetals
Nonmetals do not have characteristics of metals
DUH! So what does this mean?
They do not conduct electricity
They are not shiny
They are not malleable
Periodic Table
The elements are grouped into categories besides
metals and nonmetals
The first scientist to group elements together based
on those properties was Dmitri Mendeleev in 1869
He placed them into a table based on their atomic
masses
He noticed that a pattern in the elements that as the
atomic mass increased that they had certain
properties
Periodic Table
However, he had gaps!
So he left the gaps in the table and hypothesized that
elements that had not yet been discovered would fit
right in
AND HE WAS RIGHT! The new elements fit his pattern
They later realized that it was more useful to group
the elements based on atomic number instead of
mass and this led to what we now call the Periodic
Table
Periodic Table
Each square represents an element
Each column of the table contains elements that have
similar properties
We also call these groups or families
All the heaviest elements starting with Neptunium
(element number 93) are not naturally occurring and
are formed only in a laboratory
The rows are called periods
A zigzag line separates metals from nonmetals with
the nonmetals on the right and metals on the left!
Except for Hydrogen!
Families of Elements
Elements in the same family have the same
characteristics (except for Hydrogen , it
doesn’t fit into a family)
The first column are called the alkali metals
They react most strongly with other
elements and are so reactive they
EXPLODE! when put in water
Column 2 are the Alkaline Earth Metals that are
still reactive by not as much as the first column
They burn very brightly when heated in air
Transition Metals
Columns 3-12 all belong to the transition
metals
These elements are the metals that have the
characteristics of a metal such as luster (shiny)
and malleability!
They do not react as strongly as those in
column 2
Halogens
Group 17 are the most reactive of all the nonmetals!
They react especially strong with those in group 1
Nobel Gases
Found in column 18
They are all gases!
They are the least reactive family of all the groups in
the periodic table