2 History of the Periodic Table Antoine Lavoisier (1743 – 1794)Published Elements of Chemistry in 1789Included a list of “simple substances” (which we now know to be elements)Formed the basis for the modern list of elementsOnly classified substances as metals or nonmetals
3 History of the Periodic Table Johann Döbereiner (1780 – 1849)Classified elements into “triads”Groups of three elements with related properties and weightsBegan in 1817 when he realized Sr was halfway between the weights of Ca and Ba and they all possessed similar traitsDöbereiner’s triads:Cl, Br, I S, Se, TeCa, Sr, Ba Li, Na, K
4 History of the Periodic Table John Newlands (1837 – 1898)Law of Octaves (1863)Stated that elements repeated their chemical properties every eighth elementSimilar to the idea of octaves in music
5 History of the Periodic Table Dmitri Mendeleev (1834 – 1907)Russian chemist (“The father of the P.T.”)Arranged elements based on accepted atomic masses and properties that he observedListed elements with similar characteristics in the same family/groupLeft blank spots for predicted elements which would be discovered later
7 Dmitri Mendeleev (1834 – 1907) Property Mendeleev’s Prediction for “eka-silicon” in 1871Observed Properties of Germanium (discovered in 1886)Atomic Weight7272.59Density (g/cm3)5.55.35Melting Point (°C)High947ColorDark grayGrayish whiteFormula of oxideXO2GeO2
8 History of the Periodic Table Henry Moseley (1887 – 1915)English physicistArranged elements based on increasing atomic numberRemember: atomic number = # of p+ in nucleusPeriodic table looked similar to Mendeleev’s design since as atomic number increases, so does the atomic mass
9 Periodic Law Periodic – occurring at regular intervals Relates to trends on the periodic table of elementsModern Periodic LawWhen elements are arranged in order of increasing atomic number, there is a periodic repetition of their properties
10 Reading the Periodic Table Periods“Horizontal Rows” on the periodic tableGroups (or Families)“Vertical Columns” on the periodic table
11 Reading the Periodic Table Metalloids – elements having properties of both metals and nonmetals
12 Properties of Metals/Non-metals/Metalloids Metals - shiny, smooth, solid at room temperature, good conductors of heat and electricity, malleable and ductile.Metalloids (along stair step line) physical and chemical properties of both metals and nonmetals- B, Si, Ge, As, Sb, TeNonmetals – low melting and boiling points, brittle, dull-looking solids, poor conductors of heat and electricity.
13 Reading the Periodic Table Valence e- are periodic!Notice the similaritiesEx.) Write the noble gas configurations for:FClBrIGROUPS have similar valence electron configurations!
14 Groups of Elements Group 1 = Alkali Metals Located in Group 1 (except Hydrogen)Extremely reactiveWant to lose 1 e- to become “noble gas-like”Group 2 = Alkaline Earth MetalsAlso very reactiveBoth Group 1 & 2 occur naturally as compounds not elements
15 Group 1: Alkali Metals Li, Na, K, Rb, Cs Reaction of potassium + H2OCutting sodium metal
16 Group 2: Alkaline Earth Metals Be, Mg, Ca, Sr, Ba, RaMagnesiumMagnesium oxide
17 Groups of Elements Group 17 = Halogens Very active nonmetals Want to gain 1 e- to become like a noble gas
18 Groups of Elements Group 18 = Noble Gases Sometimes called “inert gases” since they generally don’t reactMainly true, but not always (Kr, Xe will react sometimes)Have a full valence shell (8 e-)
19 Groups of Elements Transition Metals Lanthanides and Actinides Located in the center of the Periodic Table10 elements wide (“d” orbitals)Semi-reactive, valuable, crucial to many life processesLanthanides and ActinidesLocated at the bottom of the Periodic Table14 elements wide (“f” orbitals)Some are radioactive, though not allLanthanides = Period 6Actinides = Period 7
21 Periodic Properties & Trends ElectronegativityAbility of an atom to pull e- towards itselfLinus Pauling: developed scale to demonstrate different electronegativity strengthsIncreases going up and to the rightAcross a period more protons in nucleus = more positive charge to pull electrons closerDown a group more electrons to hold onto = element can’t pull e- as closely
22 Periodic Properties & Trends ElectronegativityAbility of an atom to pull e- towards itselfAcross a period more protons in nucleus = more positive charge to pull electrons closerDown a group more electrons to hold onto = element can’t pull e- as closely
23 Periodic Properties & Trends Atomic RadiusDistance between the nucleus and the furthest electron in the valence shellIncreases going down and to the leftDown a group more e- = larger radiusAcross a period elements on the right can pull e- closer to the nucleus (more electronegative) = smaller radius*Remember*LLLL Lower, Left, Large, Loose
24 Periodic Properties & Trends Atomic RadiusIncreases goingdown and to the left*Remember*LLLL Lower, Left,Large, Loose
26 Periodic Properties & Trends Ionization EnergyEnergy required to remove an e- from the ground state1st I.E. = removing 1 e-, easiest2nd I.E. = removing 2 e-, more difficult3rd I.E. = removing 3 e-, even more difficultEx.) B --> B+ + e I.E. = 801 kJ/molEx.) B+ --> B e I.E.2 = 2427 kJ/molEx.) B+2 --> B e I.E.3 = 3660 kJ/mol
27 Periodic Properties & Trends Ionization EnergyIncreases going up and to the rightDown a group more e- for the nucleus to keep track of = easier to rip an e- offAcross a period elements on the right can hold electrons closer (more electronegative) = harder to rip an e- off
28 Periodic Properties & Trends Metallic CharacterHow “metal-like” an element isMetals lose e-Most Metallic: Cs, FrLeast: F, OIncreases going down and to the leftThink about where the metals & nonmetals are located on the periodic table to help you remember!
29 Periodic Properties & Trends Ionic RadiusRadius of an atom when e- are lost or gained different from atomic radiusIonic Radius of CationsDecreases when e- are removedIonic Radius of AnionsIncreases when e- are added
30 Sizes of IonsLi+, 78 pm2e and 3 pLi,152 pm3e and 3pCATIONS are SMALLER than the atoms from which they are formed.Size decreases due to increasing he electron/proton attraction.
31 Sizes of IonsF-, 133 pm10 e and 9 pF, 71 pm9e and 9pANIONS are LARGER than the atoms from which they are formed.Size increases due to more electrons in shell.
32 Overall Periodic Trends PropertyGroup TrendPeriod TrendAtomic RadiusIncreases going downIncreases to the leftIonization EnergyIncreases going upIncreases to the rightElectronegativityMetallic Character