Grade 9 Science
Unit 1: Atoms, Elements, and
Compounds
Chapter 2:
Elements are the
building blocks of
matter.
Elements
 A pure substance that cannot
be broken down or separated
into simpler substances.
 Made up of one kind of atom.
 More than 115 elements
known about 92 occur
naturally.
Bill Nye Video: Atoms and Elements
Chemical Symbols
One or two (sometimes 3)
letters used to represent an
element name
Standard throughout the
world
Examples: O = Oxygen
Au = Gold
Note:
If there is only one Letter in
the chemical symbol it is
always CAPITALIZED
If there are two letters, the
FIRST IS CAPITALIZED the
second is lower case
Example:
H = Hydrogen
He = Helium
Use Your Periodic Table on
page 50 to Identify the
Chemical Symbols of these
20 Need to Know Elements:
 Hydrogen
 Iron
 Sodium
 Nickel
 Potassium
 Copper
 Magnesium
 Zinc
 Calcium
 Carbon
Nitrogen
Silicon
Oxygen
Silver
Neon
Gold
Helium
Mercury
Chlorine
Lead
The Periodic Table
Organizes elements
according to their
physical and chemical
properties.
Developed by
Dmitri Mendeleev
in 1867.
Includes the element’s
name, symbol, atomic
number and atomic
mass.
ATOMIC NUMBER = # of
Protons (& Electrons in a
Neutral atom)
ATOMIC MASS = Average
mass of the atoms of an
element
MASS NUMBER
= the number of Protons
+
the number of Neutrons
= The ROUNDED atomic Mass
To find the Number of
Neutrons:
 Subtract the
Atomic number from the
rounded Atomic Mass!
# Neutrons = 16 - 8
=8
Complete the Chart:
Element
Name
Symbol
Atomic
Number
# of
Protons
# of
Electrons
Atomic
Mass
K
hydrogen
12
8
2
23.0
Elements
Metals
Metalloids
Text Page 51
NonMetals
Elements can be METALS,
NON-METALS, or
METALLOIDS
Metals
 Shiny
 Malleable
 Ductile
 Usually solid
 Good
conductors
of heat and
electricity
Non-metals
Tend to be
gases or
brittle solids
Dull
Not malleable
or ductile
Poor
conductors
of heat and
electricity
Metalloids
Solids
Shiny or dull
May conduct
electricity
Poor
conductors
of heat
Nonmalleable
and not
ductile
Properties of both metals and non-metals.
 The periodic table is
organized into periods and
chemical families.
Periods: the horizontal rows
Families: the vertical columns
 Elements in the same family
have similar physical and
chemical properties.
See video clips on YouTube:
Periodic Table of Videos
Li,
Chemical Families
Na,
Alkali Metals: Family 1
K…
 Highly

Low
melting
reactive with
points
halogens
 Soft
Reactive
with oxygen
and water
Video
Alkaline Earth Metals:
Family 2
Less reactive
then alkali
metals
Burn in air if
heated
Produce
bright
flames
React with
water
Be,
Mg,
Ca…
Halogens: Family 17
Non-metals
Highly
reactive
F is the
most
reactive
element
F,
Cl,
Br…
Noble Gases: Family 18
Very
stable
Highly
unreactive
All gases
He, Ne, Ar…
Transition Metals
Found at the
centre of the Three are
periodic table magnetic;
Complex
arrangement
Fe, Co
of electrons
and Ni
Families of the Periodic Table
Questions page
59
#’s 1-14
Section 2.3 The Periodic Table
and the Atomic Theory page 60
Bohr-Rutherford diagram
Nucleus
2e8e-
8e18e-
Electron Filling Rules:
- Use the ATOMIC NUMBER to
determine the number of electrons
and protons of the element
- Levels are filled from the INNER
most energy levels OUT.
- The First Energy level can hold a
MAXIMUM of 2 electrons
- The second and third energy levels
hold a MAXIMUM of 8 electrons
Energy Level Periodic
Trends
1. The number of Valence Electrons = the
Family Number
2. The number of Energy Levels = the
Period Number
3. The Maximum Number of Electrons in
each Level = the Number of elements in
that Period
4. Elements in the same Family have the
same number of Valence Electrons
The valence shell of the
noble gases is FULL;
therefore stable.
Gaining or losing electrons
will allow atoms to achieve
a kind of stability. Metals
will lose electrons while
non-metals will gain them.
Questions Page 67
#1-14