The Periodic Table

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The Periodic Table

Chapter 17.3

Why is the Periodic Table important
to me?


The periodic table is the most
useful tool to a chemist.


You get to use it on every test.


It organizes lots of information
about all the known elements.


It
enable scientists to study
their
physical and
chemical
properties easily



Pre
-
Periodic Table Chemistry …


…was a mess!!!


No organization of
elements.


Imagine going to a grocery
store with no organization!!


Difficult to find information.


Chemistry didn

t make
sense.

Dmitri Mendeleev: Father of the
Table


HOW He WORKED…


Put elements in rows by
increasing atomic mass
(check pattern)


Put elements in columns
by the way they reacted.





Periodic table of elements

SOME PROBLEMS…


He left blank spaces for what he said were
undiscovered elements. (Turned out he was right!)


He broke the pattern of increasing atomic weight to
keep similar reacting elements together.


The Current Periodic Table


Mendeleev wasn

t too far off.


Henry Mosely later put the elements in rows by
increasing
ATOMIC NUMBER!!


The horizontal rows are called periods and are
labeled from 1 to 7.


The vertical columns are called groups are
labeled from 1 to 18.

Parts of a periodic table


Visist

www.ptable.com

and check the parts of
the periodic table:


We have three main
parts of the periodic
table:


-

metals, non metals and
metalloids.

Metals


Are good conductor of heat and
electricity


Are shiny and sonorous


Are ductile and malleable


Are solid at room temperature
except: mercury which is liquid


Have high melting and boiling
points


Are on the left side of the periodic
table

Non
-

metals


Are bad conductor of electricity (
with the exception of carbon
graphite) and heat.


Are brittle and dull in appearance


Are generally gases with the
exception of bromine (liquid) and
some solids ( carbon, silicon,
sulfur…)


Have low melting and boiling points


Are on the right side of the periodic
table



Metalloids


Possess some properties of
metals and non metals


They are sometimes called
semi metals and are used in
semi conductors ( Si and
Ge

are used in transistors)


Located on the stair line in
the periodic table



( check figure at the right)

Periods in a periodic table


Remember that electrons
surround the nucleus, it is
very difficult to locate an
electron but electrons are
mainly found in orbit (also
called energy levels shells
). In the nucleus, we have 7
energy levels. Electrons
occupy the energy levels
close to the nucleus
because they have lower
energy.


These energy levels
show in the
peiodic

table
as the horizontal rows.


We have 7 periods in
the periodic table.( 7
energy levels)


The period of an element
is the number of shells
occupied by electrons in
an atom.


Periods in periodic table


Energy level are usually
represented by the letter “n”


Each energy level ( if n≤4)
contains : 2n² electrons.


For n≥5, check explanation.


Now, calculate the number of
electrons in each shell.

Periodic table of elements:

According to this rule:

-
First shell: 2 electrons

-
Second shell: 8 electrons

-
Third shell: 18 electrons

-
Fourth shell: 32 electrons.

However, this is not the case in
the periodic table Why? You
will be able to understand this
in grade 10 when you learn
the concept of
suborbits

and
sublevels.


Groups in the periodic table


Groups in the periodic table
represent the vertical
columns. We have 18
groups in the periodic table.


To understand the concept
group, we should know the
concept of valence
electrons.


Valence electrons are the
electrons present in the
outer shell of an atom


Groups…Here

s Where the
Periodic Table Gets Useful!!


Elements in the
same group
have similar
chemical and
physical
properties!!


(Mendeleev did that on purpose.)






Why??


They have the same
number of valence
electrons.



Families on the Periodic Table


Columns are also grouped
into families.


Families may be one column,
or several columns put
together.


Families have names rather
than numbers. (Just like your
family has a common last
name.)

Hydrogen


Hydrogen belongs to a family
of its own.


Hydrogen is a diatomic,
reactive gas.


Hydrogen was involved in the
explosion of the Hindenberg.


Hydrogen is promising as an
alternative fuel source for
automobiles

Periods in a periodic table

Alkali Metals


1
st

column on the
periodic table (Group 1)
not including hydrogen.


Very reactive metals,
always combined with
something else in nature
(like in salt).


Soft enough to cut with a
butter knife

Alkaline Earth Metals


Second column on the
periodic table. (Group 2)


Reactive metals that are
always combined with
nonmetals in nature.


Several of these
elements are important
mineral nutrients (such
as Mg and Ca

Transition Metals


Elements in groups 3
-
12


Less reactive harder
metals


Includes metals used in
jewelry and construction.


Metals used

as metal.


Boron Family


Elements in group 13


Aluminum metal was
once rare and expensive,
not a

disposable
metal.




Carbon Family


Elements in group 14


Contains elements
important to life and
computers.


Carbon is the basis for
an
entire branch

of
chemistry.


Silicon and Germanium
are important
semiconductors.

Nitrogen Family


Elements in group 15


Nitrogen makes up over
¾ of the atmosphere.


Nitrogen and phosphorus
are both important in
living things.


Most of the world

s
nitrogen is not available
to living things.


The red stuff on the tip of
matches is phosphorus.

Oxygen Family or Chalcogens


Elements in group 16


Oxygen is necessary for
respiration.


Many things that stink,
contain sulfur (rotten
eggs, garlic, skunks,etc.)

Halogens


Elements in group 17


Very reactive, volatile,
diatomic, nonmetals


Always found combined
with other element in
nature .


Used as disinfectants
and to strengthen teeth.


The Noble Gases

The Noble Gases


Elements in group 18


VERY unreactive,
monatomic gases


Used in lighted

neon


signs


Used in blimps to fix the
Hindenberg problem.


Have a full valence shell.

Periodic table of elements


Use the periodic table : find the group and the
period of the 20 first elements. Identify the
number of valence electrons for each element.

Periodic Law


PERIODIC LAW,
in chemistry, law stating that many of the
physical and chemical properties of the elements tend to recur in
a systematic manner with increasing atomic number. Progressing
from the lightest to the heaviest atoms, certain properties of the
elements approximate those of precursors at regular intervals of
2, 8, 18, and 32. For example, the 2d element (helium) is similar
in its chemical behavior to the 10th (neon), as well as to the 18th
(argon), the 36th (krypton), the 54th (xenon), and the 86th
(radon). The chemical family called the halogens, composed of
elements 9 (fluorine), 17 (chlorine), 35 (bromine), 53 (iodine),
and 85 (astatine), is an extremely reactive family.


Watch carefully the video and visit
www.ptable.com

to compare
properties of same group elements.

Electron dot diagram


Electronic configuration:

Representation of electrons in
shells around nucleus

1.
The first shell can fit up to 2
electrons

2.
The second shell can fit up to 8
electrons

3.
The third shell can fit up to 8
electrons ( remember not 18 )

4.
Use the periodic table to draw the
electronic configuration of the 20
first elements.


Electron dot diagram

Electron dot diagram


Electron dot structure is a dot
representation of the valence
electrons ( remember valence
electrons are electrons on the outer
shell).


Electron dot diagrams are used to
represent compounds such as
H
2
O( Ch 20)


Use the blank periodic and your
results in slide 33 table to write the
electron dot structure of the 20 first
elements


Electron dot structure