Chapter 6Chapter 6

Periodic Law and Periodic TablePeriodic Law and Periodic Table

Historical backgroundHistorical background

Before 1800, 23 elements knownBefore 1800, 23 elements known By 1870, 70 elements identifiedBy 1870, 70 elements identified

No pattern to tie them together knownNo pattern to tie them together known

1864, J. Newlands noticed when elements 1864, J. Newlands noticed when elements arranged by massarranged by mass 11stst and 8 and 8thth element similar element similar 22ndnd and 9 and 9thth element similar, so on. element similar, so on. He called pattern an octave. Did not work for all.He called pattern an octave. Did not work for all.

MendeleevMendeleev

Noticed patterns while writing a book on Noticed patterns while writing a book on elements.elements.

Noticed that as mass increased, there is a Noticed that as mass increased, there is a repeating of characteristics of elements.repeating of characteristics of elements.

Also realized that some elements were not Also realized that some elements were not discovered yet.discovered yet.

Predicted properties of those, and was Predicted properties of those, and was found to be correct when discovered.found to be correct when discovered.

Were some trouble spots on P.Table Were some trouble spots on P.Table (Te,I)(Te,I)

Accdg. to Mendeleev, Periodic law stated Accdg. to Mendeleev, Periodic law stated that the characteristics of the elements that the characteristics of the elements were a periodic (repeating) function of were a periodic (repeating) function of their atomic masses.their atomic masses.

MoseleyMoseley

Discovered the proton.Discovered the proton. Called the #protons the atomic number.Called the #protons the atomic number. Realized this could “fix” Mendeleev’s P.T. Realized this could “fix” Mendeleev’s P.T.

problems.problems. This changed P. Law to be based on This changed P. Law to be based on

atomic number, not mass.(Te, I switched) atomic number, not mass.(Te, I switched) ““Chemical and Physical properties repeat Chemical and Physical properties repeat

(are periodic) when arranged by at. no.”(are periodic) when arranged by at. no.”

Modern Periodic TableModern Periodic Table Has columns and rows of elements.Has columns and rows of elements. Columns are GROUPS or FAMILIESColumns are GROUPS or FAMILIES

Very similar in chem and phys. activityVery similar in chem and phys. activity Not identical, though.Not identical, though.

Rows are called PERIODSRows are called PERIODS Elements in a period are not at all alike.Elements in a period are not at all alike.

Classification of elementsClassification of elements

MetalsMetals

Left and middle of P. TableLeft and middle of P. Table Majority of elementsMajority of elements Shiny (lustrous)Shiny (lustrous) Good conductors of heat and electricityGood conductors of heat and electricity MalleableMalleable DuctileDuctile GR. IA alkali metals-most reactiveGR. IA alkali metals-most reactive GRIIB alkaline earthmetals, less reactiveGRIIB alkaline earthmetals, less reactive

Group B ElementsGroup B Elementstransition elementstransition elements

Transition metalsTransition metals Families 3-12 on PTFamilies 3-12 on PT

Inner Transition Inner Transition MetalsMetals

Lanthanide Series 4f Lanthanide Series 4f blockblock

Actinide Series 5f Actinide Series 5f blockblock

NonmetalsNonmetals

Upper right of PT.Upper right of PT. P block P block Group 7A halogensGroup 7A halogens

very reactivevery reactive Need to gain 1 eNeed to gain 1 e--

Group 8A noble gasesGroup 8A noble gases Very unreactiveVery unreactive Filled levelsFilled levels

MetalloidsMetalloids

Border of stair step line on PT.Border of stair step line on PT. Have phys. & chemical characteristics of Have phys. & chemical characteristics of

both metals and nonmetalsboth metals and nonmetals

Write E config of Main Write E config of Main Groups Groups

These groups or families of elements These groups or families of elements have similar phys. and chem. have similar phys. and chem. characteristics.characteristics.

Reason is found in their eReason is found in their e-- config. They config. They are so similar to each other.are so similar to each other.

Same number of valence (outer) eSame number of valence (outer) e-- cause cause similar reactivity.similar reactivity.

S blockS block

Group IA, IIAGroup IA, IIA Group IA [ ]sGroup IA [ ]s1 1 config.config.

Only 1 outer eOnly 1 outer e--

That eThat e- - easily losteasily lost Very reactive (most of all metals)Very reactive (most of all metals) Alkali metalsAlkali metals

Group 2A alkaline earth metalsGroup 2A alkaline earth metals 2 outer e2 outer e--

Fairly easily lost, fairly reactiveFairly easily lost, fairly reactive Config. ends in sConfig. ends in s22 (those lost) (those lost)

P block ElementsP block Elements

3A through 8A families (IIIA-VIIIA)3A through 8A families (IIIA-VIIIA) Have filled or partially filled orbitalsHave filled or partially filled orbitals Have various reactivity depending on number Have various reactivity depending on number

of outer eof outer e--

8A (noble gases)8A (noble gases) Very stableVery stable Very UNreactiveVery UNreactive Don’t need any more eDon’t need any more e-- , levels filled , levels filled

D Block ElementsD Block Elements

Transition metalsTransition metals Largest blockLargest block Have filled outer s orbital and filled or Have filled outer s orbital and filled or

partially filled d orbitals.partially filled d orbitals.

F block ElementsF block Elements

Contain inner transition metalsContain inner transition metals Have filled outer s sublevel and filled or Have filled outer s sublevel and filled or

partially filled f orbitalspartially filled f orbitals

Number of orbitals and eNumber of orbitals and e-- held: held: Sblock 1 orb/level, up to 2e in eachSblock 1 orb/level, up to 2e in each P block, 3 orb/level, up to 6e total in each levlP block, 3 orb/level, up to 6e total in each levl D block, 5 orb/level, up to 10 e total in eachD block, 5 orb/level, up to 10 e total in each F block, 7orb/level, up to 14 e total in eachF block, 7orb/level, up to 14 e total in each

Periodic TrendsPeriodic TrendsGraphing Calc ActivityGraphing Calc Activity

Many properties or characteristics of Many properties or characteristics of elements change in predictable patterns.elements change in predictable patterns.

Atomic RadiusAtomic Radius Direct measure of atom’s size.Direct measure of atom’s size. Atoms get smaller L→R on P.TableAtoms get smaller L→R on P.Table Because more proBecause more pro++ are added to nucleus to are added to nucleus to

pull more tightly on e cloud.pull more tightly on e cloud. Atoms get largerAtoms get largerbecause more levels of e because more levels of e

are added to outside. (Onion and layers)are added to outside. (Onion and layers)

Ionic RadiusIonic Radius

Atoms gain or lose e to have only filled Atoms gain or lose e to have only filled levelslevels

These + or These + or –– particles that result are IONS. particles that result are IONS. Ions will have the same no. proIons will have the same no. pro++ as atom of as atom of

that element. (Only e change)that element. (Only e change) The more e added to an atom, the larger The more e added to an atom, the larger

the ion will be. the ion will be. The more e lost, the smaller the ion.The more e lost, the smaller the ion.

SS_2_2 larger than S atom. (18 e/16e) larger than S atom. (18 e/16e) ClCl-- larger than Cl. (18e/17e) larger than Cl. (18e/17e) NaNa++ smaller than Na atom. (10e/11e) smaller than Na atom. (10e/11e) MgMg+2+2 smaller than Mg atom (10e/12e) smaller than Mg atom (10e/12e)

Ionization EnergyIonization Energy

Amount of energy needed to pull off the Amount of energy needed to pull off the outer e from an atom. (produces a + ion)outer e from an atom. (produces a + ion)

Atoms on Left of P.Table hold their e Atoms on Left of P.Table hold their e loosely and easily lose them.loosely and easily lose them.

Atoms on Right (P Block) of P.T. hold e Atoms on Right (P Block) of P.T. hold e tightly because they would rather gain tightly because they would rather gain than lose e.than lose e.

I.E. increases L→RI.E. increases L→R

I.E. decreasesI.E. decreases because as atoms get because as atoms get larger the outer e are further from the larger the outer e are further from the nucleus and attraction from pronucleus and attraction from pro++..

Octet RuleOctet Rule

We have hinted at this idea-We have hinted at this idea- Atoms tend to gain, lose, or share e to Atoms tend to gain, lose, or share e to

obtain a full set of 8 outer e (s and p obtain a full set of 8 outer e (s and p blocks)blocks)

H and He are filled with 2 e, no p block at H and He are filled with 2 e, no p block at all.all.

ElectronegativityElectronegativity

Ability of an atom to attract e to itself within Ability of an atom to attract e to itself within a chemical bond.a chemical bond.

Arbitrary units assigned to elements up to Arbitrary units assigned to elements up to 3.98 (F is most e negative )3.98 (F is most e negative )

Cs and Fr (opp corner from F) are least.Cs and Fr (opp corner from F) are least. Whichever element in bond has largest Whichever element in bond has largest

value pulls e more toward itself. (E greedy)value pulls e more toward itself. (E greedy) EN inc→, EN decEN inc→, EN dec..