Organization of the Periodic Table

Demetry Mendeleev organized the elements in the first periodic table by order of mass in

1870. Found repetition in Found repetition in

properties of elementsproperties of elements Widely accepted Widely accepted

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

Problem: elements were elements were being placed in groups being placed in groups of elements with of elements with differing propertiesdiffering properties

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

number of protons. Clear periodic patternsClear periodic patterns Mendeleev’s problems of Mendeleev’s problems of

properties are solvedproperties are solved Periodic law – there is a – there is a

periodic repetition of periodic repetition of chemical and physical chemical and physical properties of the properties of the elements when they are elements when they are arranged by increasing arranged by increasing atomic numberatomic number

The Modern Periodic Table

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

nucleus

Families

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

electrons, or valence electrons.

Families

Each family is Each family is numbered 1 through 8, followed by the letter A or B.followed by the letter A or B.

The families designated with an The families designated with an A (1A-8A) are called representative elements because they possess a wide range of because they possess a wide range of chemical and physical properties.chemical and physical properties.

Families designated with a Families designated with a B are referred are referred to as to as transition elements.

Periods

Other major divisions in the Periodic Table include the metals, nonmetals,

and metalloids

Metals

Characteristics of Metals Shiny and smoothShiny and smooth Solid at room temperatureSolid at room temperature Good conductors of heat and electricityGood conductors of heat and electricity Ductile and malleableDuctile and malleable Most group A and all group B elements are Most group A and all group B elements are

metalsmetals Group 1A elements (except H) are Group 1A elements (except H) are alkali metals Group 2A elements are alkaline earth metals;

both are chemically reactive, alkali the more reactive

Elements from group B (lanthanide series) are used as phosphors, substances that emit light when struck by e- struck by e-

Nonmetals

Characteristics of Nonmetals

Upper right side of periodic tableUpper right side of periodic table Gases or brittleGases or brittle Dull-looking solidsDull-looking solids Poor conductors of heat and electricityPoor conductors of heat and electricity Br – only nonmetal that is a liquid at room temp.Br – only nonmetal that is a liquid at room temp. Halogens – 7A, highly nonreactive Noble gases – 8A, extremely nonreactive 8A, extremely nonreactive

Metalloids

Characteristics of Metalloids

Physical and chemical properties of both Physical and chemical properties of both metals and nonmetalsmetals and nonmetals

Silicon and Germanium are two of the Silicon and Germanium are two of the most important metalloids, they are most important metalloids, they are used in computer chips and solar cells

Silicon – used in computer chips and solar cells

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 a gaseous state atomfrom a gaseous state 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