Transcript The Periodic Table - Lincoln Park High School

The Periodic Table
content
 i. Dimitri Mendeleev's periodic table
 ii. The modern periodic table
 iii. Families of the periodic table
 iv. Periodic trends
 v. Ionization energy
 vi. Ions
 vii. Valence electrons
 viii. Electronegativity
 ix. Lewis’s Octet rule
 x. Credit
Dmitri Mendeleev: Father of the
Table
HOW HIS
WORKED…
• Put elements in
rows by increasing
atomic mass.
• Put elements in
columns by the way
they reacted.
SOME
PROBLEMS…
• He left blank spaces
for what he said
were undiscovered
elements.
• He broke the pattern
of increasing atomic
mass to keep similar
reacting elements
together.
The Current Periodic Table
• Now the elements are put in rows by
ATOMIC
NUMBER
increasing
• 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.
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.
Hydrogen
Hydrogen belongs
to a family of its
own.
 Hydrogen is a
diatomic, reactive
gas.

Alkali Metals
 1st column on the
periodic table (Group
1) not including
hydrogen.
 Very reactive metals,
always combined with
something else in
nature (like in salt).
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)
Metals vs. Nonmetals
 Metals are shiny, good conductors of heat
and electricity, malleable, ductile, and form
cations (positive ions, loss of electrons)
during chemical change.
 Nonmetals are not shiny. They are poor
conductors, brittle. They frequently form
anions (negative, gain of electrons) in
chemical changes.
Transition Metals
• Elements in groups 3-12
• Less reactive harder metals
• Includes metals used in
jewelry and construction.
Metalloids
 Metalloids have some characteristics of
both metals and nonmetals. They are B,
Si, Ge, As, Sb, Te, Po, At.
Halogens



Elements in group 17
Very reactive,
volatile, diatomic,
nonmetals
Always found
combined with other
element in nature .
(CHLORINE)
The Noble Gases
AKA Inert Gases
 Elements in group
18
 VERY unreactive,
monatomic gases
 Have a full valence
shell.

Periodic Trends



Moving left to right across a period, atomic radius usually
decreases. This occurs because each successive element has an
added proton and electron which causes the electron to be drawn
closer to the nucleus.
This decrease in atomic radius also causes the ionization energy
to increase when moving from left to right across a period. The
more tightly bound an element is, the more energy is required to
remove an electron.
Similarly, electronegativity will increase in the same manner as
ionization energy because of the amount of pull that is exerted on
the electrons by the nucleus.
Summary of Periodic Trends
Ionization energy
Energy required to overcome
the attraction of the nuclear
charge and to remove an
electron from a gaseous
atom.
Ions
•
+ positive
ions - cations - always smaller than
the neutral atom from which they form because loss
of outer-shell electrons result in increased attraction
by nucleus for the fewer remaining electrons.
•  negative ions - anions - always larger than the
neutral atom because effective nuclear attraction is
less for increased number of electrons
Group trends
v.s
period trends
 Ionic radii increase as moving
down each group
 Gradual decrease in size for
both cations and anions as
moving from left to right
electronegativity
The tendency for atoms of the
element to attract electrons when
they are chemically combined with
atoms of another element
They are calculated and expressed in
arbitrary units called Paulings
Pauling electronegativity scale
• Noble gases do not form any compund
so omitted in the scale
• Electronegativiy of representative
elments(Group A elements) increases as
moving from left to right
• Metallic elements= low
• Non-metallic elements= high
• Most electronegative: Fluorine- 4.0
• Least electronegative: Cesium- 0.7
• Elctronegativity values help predict type
of bonding between atoms in
compounds.
Valence electrons

Electrons in the highest occupied
enegy level of an element’s atoms
The number of valence electrons largely determines
the chemical properties of an element
Therefore: elements within each group behave similarly
because they have the same number of V.e-
Valence electrons
• The number of valence electrons is the
same as the group number of the element.
(eg.Gr 1A elements has 1 V.e-)
• EXCEPTION: GR 0 (noble gases)- Helium has 2 V.e- and all
others have 8.
• V.e- are usually the only electrons used in chemical bonding
so only V.e- are shown in electron dot structures.
Octet rule




Gilbert Lewis, 1916
In forming compounds, atoms tend to achieve
the electron configuration of a noble gas
(ns2np6)
Atoms of metallic elements tend to lose V.e-,
leaving complete octet in next lowest energy
level
Atoms of some non-metallic elements tend to
gain e- or to share e- with another non-metallic
element to achieve a complete octet.
Credits
Powerpoint presentation designed by:
Victoria Gotay and Mengyi Xu
Content sources:
Chemistry, fifth edition, Addison-Wesley
publications
Images and graphs souces: THANK
www.webelements.com
www.wsd1.org
www.iamanangelchaser.com
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