Chapter 6Chapter 6The Periodic TableThe Periodic Table

The Periodic The Periodic TableTableDevelopment of the Periodic Table:Development of the Periodic Table:

About 70 elements were discovered before the About 70 elements were discovered before the 1880s1880s

Dmitri Mendeleev first listed elements in a Dmitri Mendeleev first listed elements in a systematic, organized way.systematic, organized way.

He arranged atoms by their properties and in order He arranged atoms by their properties and in order of atomic mass.of atomic mass.

Mendeleev constructed the first periodic table.Mendeleev constructed the first periodic table. He left blank places for unknown elements.He left blank places for unknown elements. Henry Moseley determined atomic # and arranged Henry Moseley determined atomic # and arranged

elements by this instead of atomic mass. elements by this instead of atomic mass.

The Modern The Modern Periodic TablePeriodic TableEach element is represented by its symbol Each element is represented by its symbol

and atomic number placed in a squareand atomic number placed in a square

The horizontal arrangement of elements The horizontal arrangement of elements are called are called periods.periods.

Periodic LawPeriodic Law—when the elements are —when the elements are arranged in order of increasing atomic arranged in order of increasing atomic number, there is a repeated pattern of number, there is a repeated pattern of physical and chemical properties.physical and chemical properties.

The Modern The Modern Periodic TablePeriodic Table

GroupGroup—a vertical arrangement of atoms.—a vertical arrangement of atoms.

The elements in any group have similar The elements in any group have similar chemical and physical properties.chemical and physical properties.

Each group is identified by a number and Each group is identified by a number and letter A or B.letter A or B.

The Modern The Modern Periodic TablePeriodic Table

Group A elements are known as Group A elements are known as representative elementsrepresentative elements..

Representative elements are broken into 3 Representative elements are broken into 3 classes.classes. Metals—high electrical conductivity and lusterMetals—high electrical conductivity and luster Alkali metals—Group 1AAlkali metals—Group 1A Alkaline Earth Metals—Group 2A elementsAlkaline Earth Metals—Group 2A elements

Most non-representative elements are also Most non-representative elements are also metalsmetals

The Modern The Modern Periodic TablePeriodic Table

Nonmetals—occupy upper right corner of Nonmetals—occupy upper right corner of the periodic table.the periodic table. Nonlustrous and poor conductors of electricity.Nonlustrous and poor conductors of electricity. Some are gases, some are solidsSome are gases, some are solids

2 nonmetal groups have special names2 nonmetal groups have special names Halogens—group 7A (ex. chlorine & bromine)Halogens—group 7A (ex. chlorine & bromine) Noble gases—group 8A (or group 0)Noble gases—group 8A (or group 0)

Inert gases—they do not undergo chemical Inert gases—they do not undergo chemical reactionsreactions

The Modern The Modern Periodic TablePeriodic Table

MetalloidsMetalloids—elements with properties that —elements with properties that are intermediate between metals and are intermediate between metals and nonmetals.nonmetals.

A heavy line divides metals from A heavy line divides metals from nonmetals.nonmetals.

Most elements that border this line are Most elements that border this line are metalloids.metalloids.

Periodic TrendsPeriodic TrendsPeriodicityPeriodicity—the quality of occurring —the quality of occurring at regular intervalsat regular intervals

The periodic table arranges the The periodic table arranges the elements based on the periodic elements based on the periodic nature of their chemical & physical nature of their chemical & physical properties.properties.

Trends we’ve studied so far include:Trends we’ve studied so far include: Electron configurationsElectron configurations Atomic #Atomic #

Atomic SizeAtomic SizeAtomic Size: size of elements is Atomic Size: size of elements is difficult to define because of atomic difficult to define because of atomic orbital shapes.orbital shapes.

Atomic RadiusAtomic Radius— ½ the distance — ½ the distance between the nuclei of 2 bonded between the nuclei of 2 bonded atoms.atoms.

Atomic RadiusAtomic RadiusMeasured in picometers (pm)Measured in picometers (pm) 1pm = 1 x 101pm = 1 x 10-12-12 m m

Down a Down a groupgroup, atomic radius , atomic radius increases.increases. Nucleus increases & e- occupy outer Nucleus increases & e- occupy outer

orbitalsorbitals

Across a Across a periodperiod (left to right), atomic (left to right), atomic radius decreasesradius decreases Electrons enter the same energy levelElectrons enter the same energy level The protons & electrons are pulled to The protons & electrons are pulled to

each other, so the size decreases.each other, so the size decreases.

Ionization EnergyIonization EnergyIonization EnergyIonization Energy—the energy —the energy required to remove an electron from an required to remove an electron from an atom.atom.

11stst ionization energy—the energy needed ionization energy—the energy needed to remove the 1to remove the 1stst e- from a neutral atom. e- from a neutral atom. Na Na Na Na++ + e + e--

22ndnd ionization energy—the energy needed ionization energy—the energy needed to remove 1 e- from the 1+ ion.to remove 1 e- from the 1+ ion. NaNa++ Na Na2+ 2+ + e+ e--

Ionization EnergyIonization Energy

Down a Down a groupgroup, ionization energy , ionization energy decreasesdecreases The outer eThe outer e-- are further from the are further from the

nucleus and are easier to remove.nucleus and are easier to remove.

Across a Across a periodperiod (L (LR), ionization R), ionization energy increasesenergy increases With more protons and electrons, the With more protons and electrons, the

attraction is stronger.attraction is stronger.

Ionic SizeIonic SizePositive ions (cations) are smaller than Positive ions (cations) are smaller than their neutral atom.their neutral atom. They lose the outer shell of electronsThey lose the outer shell of electrons

Negative ions (anions) are larger than Negative ions (anions) are larger than their neutral atom.their neutral atom. More electrons reduce the attraction to the More electrons reduce the attraction to the

nucleus.nucleus.

Down a Down a groupgroup, ionic size increases, ionic size increases

Across a Across a periodperiod (L(LR),R), Cation size decreasesCation size decreases Anion size decreasesAnion size decreases

ElectronegativityElectronegativityElectronegativityElectronegativity—the —the tendency for one atom to attract tendency for one atom to attract electrons when bonded with electrons when bonded with another atom.another atom. Measured in PaulingsMeasured in Paulings

Down a Down a groupgroup, electronegativity , electronegativity decreasesdecreases

Across a Across a periodperiod (L (LR) R) electronegativityelectronegativity increases increases

Periodic TrendsPeriodic Trends

Ionization EnergyIonization EnergyAtomic RadiusAtomic Radius

Cation Size Anion Size

Ion SizeIon Size

ElectronegativityElectronegativitySolubilitySolubility

DensityDensity

All arrows show increasing