SECTION 1: THE
PERIODIC TABLE
Chapter 19: Elements and their
Properties
WARM-UP
Many
parts of our lives are affected
by repeated patterns. For example, a
calendar shows the patterns of
weeks. Name some repeated
patterns that you see happening all
the time.
LEARNING GOALS
Explain
the composition of the
periodic table.
Use
the periodic table to obtain
information.
Explain
what the terms metal,
nonmetal, and metalloid mean.
ORGANIZING THE ELEMENTS
In
the late 1800s, Dmitri
Mendeleev searched for a
way to organize the
elements.
 He arranged all of the
elements known at that
time in order of increasing
atomic mass and
discovered a pattern.
ORGANIZING THE ELEMENTS
All
of the elements of the same color
show similar properties.
ORGANIZING THE ELEMENTS
When
we arrange them in rows, similar
properties align in the same column.
ORGANIZING THE ELEMENTS
Because
this pattern repeated, it was
considered to be periodic.
Periodic
Table: a table that arranges the
elements by increasing atomic number
and by changes in physical and chemical
properties.
ORGANIZING THE ELEMENTS
Mendeleev’s
table was not perfect.
 Some elements on the current periodic
table show decreasing atomic mass
from left to right.
Henry
Moseley arranged the
elements based on atomic number
instead.
 We still use this method today!
THE PERIODIC TABLE
All
of the elements in the pink
squares are metals.
 Ex: Iron, zinc, and copper
 Most metals are solids at room
temperature
 Shiny, can be drawn into wires,
pounded into sheets, and are good
conductors
THE PERIODIC TABLE
All
of the elements in the green
squares are nonmetals.
 Ex: Oxygen, bromine, and carbon
 Most nonmetals are gases
 Most are brittle, and are poor
conductors of heat and electricity
THE PERIODIC TABLE
All
of the elements in the purple
squares are metalloids.
 Ex: Boron, silicon, and arsenic
 Have some properties of both metals
and nonmetals
 Also called semimetals
THE PERIODIC TABLE
Vertical
columns of elements are
called groups or families.
 Elements in the same group have
similar chemical properties.
Horizontal
rows of elements are
called periods.
 Atomic number increases across a
period.
ELECTRON CLOUD STRUCTURE
Electrons
are responsible for giving
groups of elements similar
properties.
In
a neutral atom, the number of
electrons is equal to the number of
protons.
 A carbon atom has 6 protons and 6
electrons.
ELECTRON CLOUD STRUCTURE
Electrons
within the electron cloud
have different amounts of energy.
 We model this difference by placing
electrons into different energy levels.
ELECTRON CLOUD STRUCTURE
Energy
levels closest to the nucleus
have lower energy than those in the
outer energy level.
ENERGY LEVELS
Energy
levels are named using the
numbers 1-7.
 Each number corresponds to a row on the
periodic table.
ENERGY LEVELS
Hydrogen
and Helium are in the first row.
 Their electrons only occupy energy level 1
 Hydrogen has 1 electron in this level
 Helium has 2 electrons in this level
ENERGY LEVELS
Each
energy level has a maximum
number of electrons that it can hold
 Energy level 1 can hold 2 electrons
 Energy level 2 can hold 8 electrons
 Energy level 3 can hold 18 electrons
 Energy level 4 can hold 32 electrons
Once
one energy level is filled,
electrons start filling the next level.
ENERGY LEVELS
It
is the number of electrons in the
outer energy level that determines
the chemical properties of the
element.
 Valence electrons: the electrons that
occupy the outermost energy level.
ENERGY LEVELS
Even
though each energy level can hold a
different total number of electrons, the
outermost energy level of an atom can
only hold up to EIGHT valence electrons.
ENERGY LEVELS
All
elements in the same group have
the same number of valence
electrons.
ELECTRON DOT DIAGRAMS
Hydrogen,
lithium, and sodium all
have one electron in their
outermost energy level.
 We can show this relationship by
using electron dot diagrams.
 Electron dot diagram: uses the
symbol of the element and dots to
represent electrons in the outermost
energy level.
ELECTRON DOT DIAGRAMS
Practice:
draw the electron dot diagram
for the following elements:

Lithium (Li)

Phosphorus (P)

Bromine (Br)

Argon (Ar)

Strontium (Sr)

Oxygen (O)
ELECTRON DOT DIAGRAMS
The
elements in Group 17 have
electron dot diagrams similar to
chlorine:
 Because all members of a group have
the same number of valence electrons,
they all undergo chemical reactions in
similar ways.
ELECTRON DOT DIAGRAMS
A
common property of the elements
in Group 17 is that they easily form
compounds with elements from
Group 1.
ELECTRON DOT DIAGRAMS
 Sodium and chlorine come together to
form sodium chloride.
ELECTRON DOT DIAGRAMS
Not
all elements will combine readily
with other elements.
 Elements in Group 18 have full outer
energy levels.
This causes these elements to be relatively
unreactive.

CHECK-IN
What
do all of the elements in a
group have in common?