Science
Chapter B1
Classifying
Matter
Lesson 1: What are Elements?
Text pages B8-B15
Vocabulary
element:
a substance that cannot be broken down into other
substances by heat, light, or electricity
periodic table:
atom:
a chart that classifies elements by their properties
the smallest particle of an element that has the properties of
the element
nucleus:
proton:
the center of an atom, where protons and neutrons are
located
particle in an atom that has a positive electrical charge
neutron:
particle in an atom that has no charge
electron:
particle in an atom that has a negative electrical charge
Building Blocks of Matter
• matter = anything that has mass and takes up
space
• Everything in the world is made up of matter.
• Matter is made up of 112 substances called
elements.
• element = a substance that cannot be broken
down into another substance by heat, light, or
electricity
• aluminum, gold, iron, etc.
• Elements combine to make different kinds of
matter like letters combine to make different
words.
A History Lesson
• Some ancient people thought all things in nature
were made up of only four substances.
• earth • air
• water
• fire
• Early scientists began to recognize some
elements for what they were, and began trying to
identify all the elements.
• Substances were tested to see if they could
be broken down.
• A French scientist, named Antoine-Laurent
Lavoisier, completed the first list of elements.
• 60 elements
Properties of Elements
• Different elements have different properties.
• Metals
• Shiny
• Conduct heat and electricity
• Can be hammered or pulled into shapes
• Gold, copper, silver, iron, etc.
• Nonmetals
• Not shiny
• Do not conduct heat and electricity
• Cannot be hammered or pulled into shapes
• Oxygen, nitrogen, carbon, etc.
The Periodic Table
• Scientists tried many different ways to group the
elements.
• Dmitri Mendeleev (a Russian scientist) found a way.
• Elements numbered from lightest to heaviest
• Elements grouped by properties
• Elements placed in rows and columns (chart)
• Mendeleev saw a pattern.
• Mendeleev’s chart had holes in it that were later
filled by newly-discovered elements.
• Periodic Table of Elements
The Periodic Table
• Each box on the periodic table contains special
information about one element.
79
Au
Gold
Atomic number
• Elements are
numbered from
lightest to heaviest.
The numbers run
from 1-112.
Symbol
• Each element has a
symbol that stands
for its name. “Au”
are the first two
Name
letters of aurum, the
• Element’s name are
Latin word for gold.
often listed.
The Periodic Table
• On the periodic table, elements are grouped in
columns.
• Each column contains elements that have
similar properties.
• They may look or act similarly.
• Most metals are grouped together. The same
goes for nonmetals and man-made elements.
26
1
H
Hydrogen
Fe
Iron
86
50
Sn
Tin
Rn
Radon
101
Md
Mendelevium
Atoms
• atom = a tiny particle of matter; the smallest
particle of an element that has the properties of
the element
• The center of an atom is called the nucleus.
• Atoms contain even smaller particles.
• protons = positively charged particles found in
the nucleus of an atom
• neutrons = particles found in the center of an
atom that have no charge
• electrons = negatively charged particles that
move around outside the nucleus of an atom
Atoms
• Each atom has a certain number of protons,
neutrons, and electrons.
• The atomic number tells both the number of
protons and the number of electrons.
79
Au
Gold
Atomic number
• The atomic number of gold is
79. That tells us gold has 79
protons. Since the number of
electrons is the same as the
number of protons, we know
gold has 79 electrons.
• The number of neutrons can be different from
one atom to another.
What is this
element’s symbol?
What is the name of
this element?
19
How many electrons
does this element
have?
How many protons
does this element
have?
Potassium
What is this element’s
atomic number?
Any
Questions?