Chapter 6 The Periodic Table• Development/History of the

Modern Periodic Table • Using the Periodic Table• An Introduction to the Elements• Periodic Trends

Periodic Table Why Periodic????

The properties of the elements repeat in in a periodic way.

Invaluable tool for chemistry Used for organization

History of the Periodic Table Timeline

Trace the development of the Periodic Table by making a timeline

Aristotle Newlands Dobereiner Meyer Mendeleev Moseley

The Basics Elements are

arranged by atomic number

Typical box contains: Name of the element Symbol Atomic number Atomic mass

Periods Horizontal Rows Numbered 1-7

Groups: Vertical Columns Numbered 1-18

Interactive Periodic Tableshttp://periodic.lanl.gov/index.shtml

www.webelements.com

www.chemicool.com

http://education.jlab.org/itselemental/ele016.html

The Families of Elements http://www.privatehand.com/flash/elements.html

Classification of the ElementsMetals

Nonmetals

Metalloids

Metals

•Occupy the left side of the periodic table•Have luster, shiny•Solids at room temp except Hg•Ductile: ability to be drawn into wires•Malleable: ability to be hammered into sheets•Excellent conductors of heat and electricity•Tend to form positive ions

NonMetals Occupy the right side of the Periodic Table

Generally gases or brittle solids

Dull-lookingBrittle Poor conductors of heat and

electricityBromine is the only liquid

at room tempTend to form negative ions

Metalloids

Characteristics of

metals and nonmetals

Classification of the Elements

Families of elements share the same ending electron configuration therefore they share similar chemical

characteristics

Valence Electrons: electrons in the highest principal energy level Determine Chemical reactivity Elements in a group share the same number of

valence electrons

The s, p, d and f blocks

Number of Valence Electrons

Elements on the left •Metals •3 or less valence electrons •tend to lose valence electrons •form positive ions

Elements on the right •Nonmetals•4 or more valence electrons•tend to gain electrons •become negative ions

Most Common Ions

Families of elementsElements of the same family (group)

share structural and chemical (behavioral) characteristics Alkali Metals Alkaline Earth Metals Transition Elements Halogens Nobel Gases

Group 1: Alkali MetalsSoft, highly reactive

metalsUsually stored under

oil or kerosene to prevent their interaction with air and water

Properties of Alkali MetalsReact vigorously with waterOxidize readily in airGood conductors of electricity

Alkali Metals Have one valence electron Will lose this electron very

easily when electron is lost the metal

gains a stable non-reactive noble gas configuration

Comparison of the Reactivity of the Alkali Metals http://www.youtube.com/watch?v=uixxJtJPVXk

Group 2: Alkaline Earth MetalsHarder, denser, stronger, and have

higher melting points than alkali metalsAll are reactive not as reactive as group 1

Alkaline Earth Metals Must lose two electrons to gain a stable

configuration

Groups 3-12:Transition Metals Not as reactive as Groups 1 and 2 Huge variety but all shiny Multi valent…form multiple ions d-block elements Also include: Inner Transition Elements (Rare

Earth Elements) Elements 58-71 Lanthanides Elements 90-103 Actinides

Group 17: HalogensMost reactive non-metalsCombine easily with metals; especially

the alkali metals

Halogens7 valence electrons, one short of a stable

octet.Will gain one electron to become stable -1 ions

Reaction of chlorine (a halogen) with sodium (an alkali metal) https://www.youtube.com/watch?v=1xT4OFS03jE

Element Dating

HydrogenMost common element in the universeChemical family by itself because it

behaves so differentlyReacts with most other elementsRarely found in a free state in nature1 valence electron

The Hindenberg Filled with H Very reactive with

oxygen gas He used in blimps

today much less reactive

than H

Group 18: Noble GasesVery low reactivityFilled valence shells: s and p levels in

the highest principal energy levels are full

Very stable electron configurationMany uses: signs, weather balloons and

the airships (Blimps)

The Octet Rule Atoms tend to gain, lose or share electrons in

order to acquire a full set of eight valence electrons.

Elements on the left (metals) tend to lose valence electrons and form positive ions

Elements on the right (nonmetals) tend to gain electrons to become negative ions

Periodic TrendsProperties of Elements tend to occur in

a predictable wayKnown as a trend, as you move across

a period or down a groupKnowing element trends allows us to

make predictions about an element’s behavior

Periodic Properties

Properties Atomic Radius Ionic Radius Electronegativity Ionization Energy

Questions we will answer: Definition How does the

property vary across the table?

Why? How does it vary

down a group? Why?

• For elements that occur as molecules, the atomic radius is half the distance between nuclei of identical atoms.

Atomic Radius

Atomic RadiusThe atomic radius is a measure of

the size of an atom.The larger the radius, the larger is

the atom.

Trends in Atomic RadiusThere is a general decrease in atomic

radius from left to right, caused by increasing positive charge in the nucleus.

Valence electrons are not shielded from the increasing nuclear charge because no additional electrons come between the nucleus and the valence electrons.

Trends in Atomic RadiusThe atomic radius decreases as

you move across a periodWhy?Increased nuclear charge pulls the

electrons in tighterAdded electrons are in the same

principal energy levels

Group Trends in Atomic RadiusAtomic Radius increases as you move

down a groupWhy?

The increasing number of electrons are in higher energy levels and instead of pulling the electrons closer to the nucleus we see the …

Atomic Radius

• Atomic radius generally increases as you move down a group.

• The outermost orbital size increases down a group, making the atom larger.

Shielding Effect

More inner electrons shield the outer electron from the nucleus and reduce their attraction to the nucleus therefore the overall atomic radius is larger

Ionic RadiusAtoms can gain or lose electrons to

form ions Ion: an atom with a charge

Recall that atoms are neutral in charge, If an electron is lost, then the overall

charge is positive If an electron is gained the atom

becomes negative

Positive Ion (Cation) Formation When atoms lose electrons

Radius always becomes smaller Because…

The loss of a valence electron can leave an empty outer orbital resulting in a small radius.

Electrostatic repulsion decreases allowing the electrons to be pulled closer to the radius.

Negative Ion (Anion) Formation

When atoms gain electrons Radius always increases Why?

More electrons mean more electrostatic repulsion resulting in increased diameter.

Period Trend for Ionic Radius As you move left to

right across a period the ionic radius gets

smaller for the positive ions

The ionic radius for the negative ions also decreases

Group Trend for Ionic Radius Both positive and

negative ions increase in size moving down a group.

Ionic Radius

Ionization Energy the amount of energy need to remove

an electron from a specific atom or ion in its ground state in the gas phase

High Ionization Energy: atom is holding onto electrons very strongly

Low Ionization Energy: atom is holding electrons less tightly

For any element (A) the process of removing an electron can be represented as follows:

A + energy -----> A+ + e-What is the periodic trend in

ionization energy? Why?

Trends for Ionization Energy

Generally increases as you move across a period because increased nuclear charge causes

an increased hold on the electrons

Ionization Energy decreases as you move down a group due to increasing atomic size

Successive Ionization Energies There is an ionization energy for each

electron that is removed from an atom After the valence electrons are removed

Ionization Energies Jump Dramatically First Ionization Energy: removes 1 electron Second Ionization Energy: removes a second

electron Third Ionization Energy: removes a third electron

Comparing Successive Ionization Energies

Trends in Ionization Energy

Electronegativity The ability of an an atom to attract electrons

to itself when it is combined with another atom

Expressed in terms of a relative scale: fluorine is assigned a value of 4 and all other elements are calculated relative to this.

The units of electronegativity are arbitrary units called Paulings.

Noble gases have no values because of few chemical compounds

ElectronegativityGreater the electronegativity

the higher an atom’s ability to pull an electron to itself when it is bonded to another atom

What are the periodic trends in electronegativity?

Why?

Trends in Electronegativity Electronegativity Increases as you move

across a period

Electronegativity decreases you move down a group

Where are the elements with highest electronegativity?

Where are the elements with lowest electronegativity?

Electronegativity

Summary of Trends

Another Summary