Organization of the Periodic Table

Dmitri Mendeleev organized the elements in the first periodic table by order of increasing

mass in 1870. Found repetition in Found repetition in

properties of elementsproperties of elements Widely accepted because Widely accepted because

it was able to predict the it was able to predict the existence and properties existence and properties of undiscovered elementsof undiscovered elements

Medeleev’s tableMedeleev’s table Arranged by increasing Arranged by increasing

atomic massatomic mass Showed periodic patternShowed periodic pattern Left blank spaces and made Left blank spaces and made

very accurate predictions very accurate predictions about the missing elements about the missing elements and their properties and their properties

Problems with Mendeleev’s Problems with Mendeleev’s TableTable

Several elements were discovered after his Several elements were discovered after his table was publishedtable was published

The atomic masses for known elements The atomic masses for known elements were more accurately determinedwere more accurately determined

It became apparent that several elements in It became apparent that several elements in his table were not in the correct orderhis table were not in the correct order

Arranging the elements by mass put them Arranging the elements by mass put them in groups that did not have the same in groups that did not have the same propertiesproperties

In 1913 Henry Mosley, an English Chemist, reorganized the Periodic Table based on the

number of protons. Discovers that atoms of each Discovers that atoms of each

element contain a unique number element contain a unique number of protons in their nucleiof protons in their nuclei Number of protons = atomic numberNumber of protons = atomic number Arranging elements in order of Arranging elements in order of

increasing atomic number solved the increasing atomic number solved the problems with elements in the table problems with elements in the table being out of order (as with atomic being out of order (as with atomic mass)mass)

Showed a clear periodic pattern of Showed a clear periodic pattern of propertiesproperties

Led to the development of the Led to the development of the periodic lawperiodic law

The Modern Periodic TablePeriodic law – there is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number

Elements are placed on the Periodic Table based on the number of protons in their

nucleus

Arrangement of Table… families

Consists of boxes – each box Consists of boxes – each box represents a single elementrepresents a single element

Columns of boxes = groups (families)Columns of boxes = groups (families) Have the same number of valence electronsHave the same number of valence electrons Have similar end electron configurationsHave similar end electron configurations Have similar chemical and physical Have similar chemical and physical

propertiesproperties

Each element in a particular family contains the same number of outer shell

electrons, or valence electrons.

Arrangement of Table cont’d … Periods

Rows of boxes = Rows of boxes = periodsperiods Represent an energy Represent an energy

level around the nucleuslevel around the nucleus period 1 = energy level 1period 1 = energy level 1

As you move across the As you move across the period (left to right), period (left to right), there is an increasing there is an increasing number of valence number of valence electronselectrons

Types of Elements

Representative elements – Groups 1A-8A – Groups 1A-8AOften referred to as the main group of elementsOften referred to as the main group of elementspossess a wide range of chemical and physical possess a wide range of chemical and physical

propertiespropertiesTransition elements – Groups 1B-8B– Groups 1B-8B

Also known as the transition metalsAlso known as the transition metalsMore recent numbering system – classifies More recent numbering system – classifies

groups as 1-18groups as 1-18

Classifying ElementsOther major divisions in the Periodic Table

include the metals, nonmetals, and metalloids

Metals Nonmetals Metalloids

Silicon – used in solar cells and computer chips

Classifying Elements MetalsMetals

Shiny, good conductors, solid at room temperature, Shiny, good conductors, solid at room temperature, ductile and malleableductile and malleable

Most elements on the periodic table are metalsMost elements on the periodic table are metals MetalloidsMetalloids

Found on stair-step line separating metals and Found on stair-step line separating metals and nonmetals in the periodic tablenonmetals in the periodic table

Only exception is AluminumOnly exception is Aluminum Have chemical and physical properties of both metals Have chemical and physical properties of both metals

and nonmetalsand nonmetals NonmetalsNonmetals

Generally gases or brittle, dull-looking solidsGenerally gases or brittle, dull-looking solids Poor conductors of heat and electricityPoor conductors of heat and electricity

Groups of ElementsGroups of Elements

Alkali metals – Group 1A ( very reactive)Alkali metals – Group 1A ( very reactive) Alkaline earth metals – Group 2A (reactive)Alkaline earth metals – Group 2A (reactive) Transition metals – B groupsTransition metals – B groups Inner Transition metals – bottom two rowsInner Transition metals – bottom two rows

Lanthanide and Actinide seriesLanthanide and Actinide series Boron Family – Group 3ABoron Family – Group 3A Carbon Family – Group 4ACarbon Family – Group 4A Nitrogen Family – Group 5ANitrogen Family – Group 5A Oxygen Family – Group 6AOxygen Family – Group 6A Halogens – Group 7A (extremely reactive)Halogens – Group 7A (extremely reactive) Noble Gases – Group 8A (nonreactive)Noble Gases – Group 8A (nonreactive)

Atomic Radius

How closely an atom How closely an atom lies to a neighboring lies to a neighboring atomatom

Trends within Trends within periodsperiods = = decreasedecrease due to due to outermost e- being outermost e- being pulled toward nucleuspulled toward nucleus

Trends within Trends within groupsgroups = = increaseincrease due to due to shielding and increased shielding and increased energy levelsenergy levels

Atomic radiusAtomic radius

Atomic RadiusAtomic Radius

Ionic RadiusIonic Radius

IonIon=atom that has a + or – =atom that has a + or – charge due to the gain or charge due to the gain or loss of e-loss of e-

Lose e-/ + charge / smaller Lose e-/ + charge / smaller atom - atom - electrostatic repulsionelectrostatic repulsion decreases & valence e- decreases & valence e- leaves unfilled orbital leaves unfilled orbital

Gain e-/ - charge /Gain e-/ - charge / larger larger atom – electrostatic atom – electrostatic repulsion increases & repulsion increases & causes increase distance causes increase distance between outer e- causing between outer e- causing larger radiuslarger radius

Ionic radiusIonic radius

Ionic radiiIonic radii

Trends within Trends within periods periods = size of the + ion = size of the + ion decreasesdecreases, then beginning in group 5A or , then beginning in group 5A or 6A the larger – ion decreases6A the larger – ion decreases

Trends within Trends within groupsgroups = ion size = ion size increasesincreases due to the ion’s outer e- being in higher due to the ion’s outer e- being in higher energy levelsenergy levels

Ionization energyIonization energy is the energy is the energy required to remove an electron required to remove an electron

from an atomfrom an atom

Ionization EnergiesIonization Energies

Ionization energyIonization energy

11stst, 2, 2ndnd , 3 , 3rdrd etc. etc.How strong atom’s nucleus holds onto the How strong atom’s nucleus holds onto the

valence e-valence e-Large ionization energy, less likely to form Large ionization energy, less likely to form

+ ions+ ionsLow ionization energy, atom loses outer e- Low ionization energy, atom loses outer e-

easily and easily forms + ionseasily and easily forms + ions

Ionization Energy TrendsIonization Energy Trends

Trends within Trends within periods periods = = increaseincrease due to due to increase in nuclear charge producing an increase in nuclear charge producing an increased hold on valence e-increased hold on valence e-

Trends within Trends within groupsgroups = = decreasedecrease due to due to valence e- being farther from the nucleus valence e- being farther from the nucleus requiring less energy to remove themrequiring less energy to remove them

Octet RuleOctet Rule

Atoms tend to gain, lose, or share e- in order to Atoms tend to gain, lose, or share e- in order to acquire a full set of eight valence e-acquire a full set of eight valence e-

Exception : 1Exception : 1stst period completely filled with 2 e- period completely filled with 2 e- Elements on the right side of the periodic table Elements on the right side of the periodic table

tend to gain e- and tend to form – ionstend to gain e- and tend to form – ions Elements on the left side of the periodic table Elements on the left side of the periodic table

tend to lose e- and form + ionstend to lose e- and form + ions

ElectronegativityElectronegativity is is how much atoms pull how much atoms pull electrons away from electrons away from another atomanother atom

Electronegativity ValuesElectronegativity Values

Electronegativity TrendsElectronegativity Trends

Trends within Trends within periodsperiods = = increaseincreaseTrends within Trends within groupsgroups = = decreasesdecreasesLowest electronegativities are found at the Lowest electronegativities are found at the

lower left side of the periodic tablelower left side of the periodic tableHighest electronegativities are found at the Highest electronegativities are found at the

upper right side of the periodic tableupper right side of the periodic table