Utilizing theperiodictable

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The Periodic Table and
Chemical Periodicity

AP Ch i t R id Learning Series
Chemistry Rapid L
i
S i
Wayne Huang, PhD
Kelly Deters, PhD
Russell Dahl, PhD
Elizabeth James, PhD
Debbie Bilyen, M.A.

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© Rapid Learning Inc. All rights reserved.

1


Learning Objectives
By completing this tutorial you will learn…
The organization of the
periodic table.
table
How properties of an
element can be determined
from trends of the periodic
table.
How electronegativity,
ionization energy electron
energy,
affinity relate to atomic
radii.
How ionic radii relates to
atomic radii.
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Concept Map
Previous content
Chemistry

New content
Studies

Matter
One type of is

Periodic
Table

Organized on

Elements

Atomic
Mass

Used to predict properties of elements according to trends

Atomic
Radii

Electronegativity

Ionization
Energy

Electron
Affinity

Ion Charge
& Radii

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2


History of the
Periodic Table

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Development of the Modern Table
Scientists went through many revisions to arrive at
the current Periodic Table.
Many scientists
organized the elements
in different ways.
Mendeleev organized the
elements by atomic
mass in rows/columns
g
p p
according to properties.

Some holes were left if no
known element had the
properties needed to fit
p
the pattern.

More elements were
discovered.

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These systems had
various flaws.

The holes were filled in.

Elements were reorganized by atomic
number.

A couple of elements
switched places.


3


Organization of
the Periodic Table
of Elements

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Definition: Periodic Table
Periodic Table – A tool used
by chemists. Organizes the
elements and provides
information about them.
Elements are organized by
increasing order of atomic
number.
The atomic number is the
number of protons and
determines the identity of
the atom.
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4


Groups and Periods
The periodic table is organized by:

Periods
Rows are called
“periods”

Groups
Columns are called
“groups” or “families”
groups
families

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Information for Each Element
Most periodic tables give the following information,
but it can be in a different location.

Element Symbol
If there’s a second
letter, it’s lowercase.

Atomic Mass
Number with decimals.
Give the mass for 1 mole
of atoms.

12
C
Carbon
C b
12.01

Atomic Number
Whole
Wh l number—
b
elements are ordered
by this on the
periodic table.

Element Name
El
tN

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5


Metals and Non-Metals
The stair-step separates the metals & non-metals.
Metalloids touch the stair-step.
Most active
non-metals
non metals

Most active
metals
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Properties of Metals and Non-Metals
There are several characteristics of each type of
element:
Metals

Non-Metals

High electrical
conductivity

Low electrical
conductivity

High melting
points

Low melting
points

Malleable &
ductile

Metalloids

Brittle
Bi l

Have
properties of
both metals
and nonmetals

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6


How to Memorize
the Elements 1-20

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Mnemonic for the First 20 Elements

Happy H
H
Henry, Th Li l B
The Little Beach B
h Boy, C N dO FiN
CaN
FiNe;
Naughty Megan, the Alpine
Sister, Pretends to Ski at ClArK Canyon
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7


Periodicity

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Definition: Periodicity
Periodicity of the Periodic Table – The
predictable pattern by which properties of
elements change across or down the
l
t h
d
th
periodic table.
There are always
exceptions to these
periodicity trends… each of
the trends is a “general”
trend as you move across a
period or down a group.

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8


Atomic Mass

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Definition: Atomic Mass
Atomic Mass – the mass in grams for
6.02 × 1023 atoms. Found on the
periodic table.

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9


Atomic Mass Trends
In general, the atomic mass:
Increases

Increases

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Atomic Mass Trends Reasoning
Why does atomic mass increase across a period?
Moving left to right, the number of protons, neutrons and
electrons all increase.
More subatomic particles leads to higher mass.
M
b t i
ti l l d t hi h

Why does atomic mass increase down a group?
For the same reason as above!
e
e

n
p
n p
n p

e

Move across the
periodic table
Mass increases

Lithium atom

e
e

pn
p p
nn p
n
e

e

Beryllium atom

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10


Atomic Radii

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Definition: Atomic Radius
Atomic Radius – Half of the distance
between the nuclei of two bonded
b t
th
l i ft
b d d
atoms.

H

H
Distance between nuclei
Atomic radius of hydrogen atom

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11


Atomic Radii Trends
In general, atomic radii:
Decreases

Increases

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Atomic Radii Trends Reasoning - 1
Why does atomic radii decrease across a period?
Moving left to right, the number of protons, neutrons and
electrons all increase.
e

e
e

n
p
n p
n p

e

Move across the
periodic table
Radius decreases

Lithium atom

e

e

pn
p p
p
n
n n

e

Beryllium atom

As the # of protons and electrons increase, the attraction
between the positive nucleus and negative electron cloud
increases.
This attraction “pulls” in on the electrons.
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12


Atomic Radii Trends Reasoning - 2
Why does atomic radii increase down a group?
Protons, neutrons and electrons are also added as you
move down a group.

e

e

Move down the
periodic table

e

+

e
e

Radius increases

e

e
e

e

e

+
e

e
e

e

Lithium atom
Sodium atom
However, the electrons are added in new energy levels.

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The inner electrons “shield” the new outer electrons from the
pull of the nucleus, therefore it doesn’t pull in like the last slide.

Electronegativity

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13


Definition: Electronegativity
Electronegativity – The pull an atom
has on the electrons it shares in a
bond with another atom.

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Electronegativity Trends
In general, electronegativity:
Increases

Decreases

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14


Electronegativity Trends Reasoning - 1
Why does electronegativity increase across a
period?
Moving left to right, the radius of the atom decreases as
more protons pull on more electrons.
Move across the
periodic table

e
e

n
p
n p
n p

e

e
e

pn
p p
p
n
n n

Radius decreases
e

Electronegativity increases

Lithium atom

e

Beryllium atom

When an atom is smaller, the electrons are closer to the
nucleus, and therefore feel the pull more strongly.
Smaller atoms will have a higher electronegativity.
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Why does electronegativity decrease down a
group?
As you move down a group, the radius increases as more
electrons shells are added
added.

e

e

e

+

Move down the
periodic table

e
e

Radius increases
Electronegativity decreases

e

e
e

e

e

+
e

e
e

e

Lithium atom
Sodium atom
As the outer electrons (those involved in bonding) are farther
from the nucleus, they will feel the “pull” of the nucleus less.
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Larger atoms have lower electronegativity.


15


Ionization Energy

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Definition: Ionization Energy
Ionization energy – The energy
needed to remove the outermost
electron.

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16


Ionization Energy Trends
In general, Ionization Energy:
Increases

Decreases

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Ionization Energy Trends Reasoning - 1
Why does Ionization Energy increase across a
period?
Move across the
periodic table

e
e

n
p
n p
n p

e

e
e

Radius decreases
IE increases

Lithium atom

e

pn
p p
p
n
n n

e

Beryllium atom

It is harder to pull electrons away from these smaller atoms.
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17


Why does electronegativity decrease down a
group?
electrons shells are added
added.

e

e

Move down the
periodic table

e

+

Radius increases
IE decreases

e
e

e

e
e

e

e

+
e

e
e

e

Lithium atom
Sodium atom
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It is easier to remove an electron from a larger atom.

Electron Affinity

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18


Definition: Electron Affinity
Electron Affinity – The energy
released when an electron is added
to an atom.

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Electron Affinity Trends
In general, electron affinity:
Increases

Decreases

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19


Electron Affinity Trends Reasoning - 1
Why does Electron Affinity increase across a
period?
Move across the
periodic table

e
e

n
p
n p
n p

e

e
e

pn
p p
p
n
n n

Radius decreases
e

EA increases

Lithium atom

e

Beryllium atom


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A smaller atom can handle an extra electron more easily as it
can be more “controlled” by the closer nucleus.

Electron Affinity Trends Reasoning - 2
Why does electron affinity decrease down a group?
electrons shells are added.

e

e

e

+

Move down the
periodic table
Radius increases
EA decreases

e
e

e

e
e

e

e

+
e

e
e

e

Lithium atom
Sodium atom
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The larger atom is less able to “control” a new electron added.


20


Ionic Charge & Radii

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Definition: Ion
Ion – Atom with a charge.
Cation – Positively charged
ion. Results from loss of
electrons.
Anion – Negatively charged
ion. Results from gain of
electrons.

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21


Predicting Ion Charge
Some ion charges can be determined from the
element’s placement on the periodic table.

Periodic Table - Charges of Common Ions
H+
Li + Be 2+

N3-

Na + Mg2+
K+ Ca 2+

F-

P3-

Al3+

O2S2-

Cl -

Zn2+ Ga 3+

Rb+ Sr2+

Se 2- Br-

Ag+ Cd2+

I-

Cs+ Ba 2+
Fr+ Ra 2+

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Ionic Radii - Cations
How does the radius of a cation compare to the
parent atom?
Atoms lose electrons to create positive ions.

e

e

e

+

Creating a cation,
losing electrons
Radius decreases

Lithium atom

e

e

+

Li+ ion

When electrons are lost, there are now more protons than
electrons.
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Therefore, the protons have a greater “pull” on each of the
electrons.


22


Ionic Radii - Anions
How does the radius of an anion compare to the
parent atom?
Atoms gain electrons to create negative ions.
e

e
e

e

e

+

e

e

Creating an anion,
gaining electrons
e
e

e

+

Radius increases

e

e

e

e

e
e

e

Oxygen atom

e

O2- ion

When electrons are gained, there are now more electrons than
protons.
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Therefore, the protons have a weaker “pull” on each of the
electrons.

Trend Summary and
Examples

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23


Summary of Trends
In general:
Atomic Mass: Increases
Atomic Radii: Decreases
Electronegativity: Increases
Ionization Energy: Increases
Electron Affinity: Increases
Atomic Mass: Increases
Atomic Radii: Increases
Electronegativity: Decreases
Ionization Energy: Decreases
Electron Affinity: Decreases

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Don’t memorize them all… understand the reasoning behind
the atomic radii trend, and know the definitions of the other
terms...then you can reason out their trends as well.

Example - 1
Example:

List Li, Cs and K in increasing order of:
These elements are in the same group.

A: Atomic radii
Li < K < Cs

Radii of the atom
As you move down a group, electron shells are added.
This makes a larger atom.
The element at the top will be the smallest.

B: Electronegativity Pull an atom has on electrons it shares in a bond.
As you move down a group, atoms get larger.
The larger the atom, the less pull on the electrons.
Cs < K < Li
Smallest atom will have the highest electronegativity.
C: Ionization Energy Energy needed to remove the outermost electron.
electron
Cs < K < Li
Smallest atom will have the highest ionization energy.
D: Electron Affinity
Cs < K < Li
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Energy released when another electron is added.
Smallest atom will have the highest electron affinity.


24


Example - 2
Example:

Put in order of increasing size: Ca, Ca2+ and Ca+.

Cations are formed by removing electrons
electrons.
When electrons are removed, there are more protons per electron.
The pull on each electron from the nucleus is now greater.
The cation will be smaller than the parent atom.
Ca2+ < Ca+ < Ca

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The Periodic Table &
The AP Exam

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25


Periodicity in the Exam
Common periodicity problems:
Which property does which trend
Definitions of the trends (ionization energy, electron
affinity, etc.)
Explain properties of elements based on periodic
trends (in free response section).

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Multiple Choice Questions
The multiple choice periodicity questions tend to be
straight-forward.
Example:
E
l

As you move down the periodic table from element 3
to element 55, the ionization energy ____.
A.
B.
C.
D.
E.

Increases
Decreases
Remains constant
Increases then decreases
Decreases then increases

Answer: B. Decreases

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26


Another Multiple Choice Question
Some questions are “definition” type questions.

Example:
E
l

The energy needed to remove the outermost electron
is ____.
A.
B.
C.
D.
E.

Electron Affinity
Activation Energy
Ionization Energy
Enthalpy of Formation
Electronegativity

Answer: C. Ionization Energy

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Free Response Questions
The Free Response questions often ask for you to
explain certain behavior.
Example:

Explain the following in terms of atomic or molecular
structure:
A. The second ionization energy of Mg is much lower
than the second ionization energy of Na
B. The atomic radius of N is greater than O
C. The boiling point of H2O is higher than H2S
D. The bond angle of NH3 is smaller than NH4+

Periodicity questions are often combined with subquestions asking about properties dependent on
bonding theory or intermolecular forces (covered
in future tutorials).
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27


Answering Free Response Questions
Be sure to thoroughly EXPLAIN…not just rephrase!
Explain the following in terms of atomic or molecular structure:
A. The
A Th second ionization energy of Mg is much lower than the second
d i i ti
fM i
hl
th th
d
ionization energy of Na
Removing the second electron from Na requires removing an
electron from a full, more stable electron shell. Removing the
second electron from Mg does not. Therefore, it takes more energy
to remove the 2nd electron from Na than Mg.
B. The atomic radius of N is greater than O

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N has fewer protons and electrons than O, although both use the
same highest energy subshell. The fewer protons and electrons in
the N atom have less of an attraction as the greater number of
protons and electrons in the O (the electrons are in the same
energy level and thus no more shielded). Therefore, the radius of
the N is larger.

Learning Summary
Other periodic trends
(Electronegativity,
Ionization Energy
and Electron Affinity)
can be reasoned
through using the
atomic radii trend.

The periodic
table
t bl organizes
i
the elements by
atomic number.

The periodic table can
be used to determine
chemical properties of
an element based on
periodic trends.

Ions gain or lose
electrons to form a
g
charge. Cations
are smaller and
anions are larger
than the “parent”
atom.

Radii decreases across
the periodic table and
increases down the
periodic table.

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28


Congratulations
You have successfully completed
the tutorial

Periodic Table and
Chemical Periodicity

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Chemistry :: Biology :: Physics :: Math

What’s N t
Wh t’ Next …

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Utilizing theperiodictable

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