Periodic Table – Let’s Sum it Up.

COLUMNS

=

FAMILIES

ROWS = PERIODSHow many periods are there in the table?

How many groups or families are present?

Bohr’s Atomic Model

• The electrons of an element’s atom fill different energy levels, starting with the first energy level.

• Elements in the same period are similar in that their last electrons are in the same energy level.

Period 1

Period 2

Period 3

Period 4

• Elements in the s and p block follow fairly typical trends. They are called the MAIN GROUP ELEMENTS. CIRCLE THEM.

• Placement of the f-block

Main Group Elements

• For the main group elements (not including transition metals) we can observer periodic trends.– Valence electrons– Ion Charge– Atomic Radius– Ionic Radius– Ionization Energy– Electronegativity

Similarities in Properties• Elements in group 17 are called

__________________________• Why are they in a group together? (2 reasons)

Atomic RadiusAtomic Radius: measure of size of an atommeasured as half the distance between nuclei of bonded atoms

Atomic Radius – what do you expect to happen?

• SHIELDING EFFECT – inner energy electrons block the nuclear pull on the outer energy electrons.

• As we go down a family from top to bottom, the principle energy level increases.

• So, the atomic radius should also _________________________.

Atomic Radius – HOWEVER…

• As we go across a period, the electrons remain in the same principal energy cloud, but the number of protons increases. So there is a stronger NUCLEAR CHARGE.

• So, as we go across a period, the atomic radius _________________________ from left to right.

Trend in Atomic Radius:

Trends in Atomic Size6.3

Size generally ____________________ across a period.

Siz

e ge

nera

lly _

____

____

____

____

___

dow

n a

grou

p pe

riod.

Valence Electrons• Octet Rule: atoms are typically very stable when they have

a full valence shell of 8 electrons. Atoms will lose or gain electrons to complete the octet.

– Why are the noble gases so stable?

– What will alkali metals do to become stable?

– What will alkaline earth metals do to become stable?

– What will halogens do to become stable?

– What will chalcogens do to become stable?

– What about noble gases?

Ionic Radius - prediction

• If an atom loses an electron and becomes a _______________, the size of the ion should be _______________ than the original atom.

• Why?

• But, if an atom gains an electron and becomes an __________, the size should be ____________ than the original atom.

• Why?

What type of elements form cations that are smaller?

6.3

What type of elements form anions that are bigger?

6.3

Trend in Ionic Radius:

First Ionization Energy• The energy required to

remove the outermost electron from an atom.

• SHIELDING EFFECT - the inner energy level electrons in an atom block the nuclear pull on the outer electrons.

• Which element do you think will have the lowest ionization energy? (The one who gives it up the easiest.)

Li

Na

K

Rb

Cs

First Ionization Energy: measure of energy required to remove outermost electron from a gaseous atom

Trend:

Causes-Trend within period: increases from left to right because of increased nuclear charge causes increased hold on outer most electronsTrend within group: decreases from top to bottom because the increase of principal energy levels means electrons are further from the nucleus with more electrons in between sheilding the force of the nucleus

______________________ across periods__

____

____

____

____

___

dow

n a

grou

p

Trend in Electronegativity:Electronegativity: ability of an atom to attract electrons in a chemical bond

Causes-Trend within period: increases from left to right because nearness to octet dictates level of attraction for bonded electronsTrend within group: decreases from top to bottom because the increase of principal energy levels means electrons are further from the nucleus with more electrons in between sheilding the force of the nucleus

Some other loose ends…

• Diatomic elements• Exceptions to anticipated electron

configurations• Tour of the Periodic Table• www.ptable.com• http://video.about.com/chemistry/Video--Tre

nds-in-the-Periodic-Table.htm

Diatomic Molecules

• When 2 atoms of the same element share electrons and are chemically bonded

• Examples existing in nature:– Cl2 I2 F2 Br2 O2 H2 N2

• All gases except for Bromine (liquid)• Where are they on the periodic table?

• Based on what we know about periodicity and valence electrons why might they combine?

Electron Configuration Exceptions• List the elements written on the board.

• Draw an orbital diagram for the outer most electrons.

• Explain why these don’t follow convention.