2History of the Periodic Table *Antoine Lavoisier(France, 1789)Earned reputation as“father of chemistry”Established a commonnaming system of compoundsand elements.First to organize elementsGrouped them into fourcategories:Gases, nonmetals, metals and “earths” (elements that could not be chemically separated at the time.)
3History of the Periodic Table Dmitri Mendeleev(Russia, 1869)1.Placed elements in groups in whichthey shared similar properties which resulted in order ofincreasing atomic mass with a few exceptions.2. Ex: If placed solely by atomic mass, iodine wasnot in group with chemically similar elements.3. Left gaps for not-yet-discovered elements and predicted their properties: gallium, germaniun & scandium.
4History of the Periodic Table Henry MoselyMoseley (1911) modified the table by organizing elements in order of increasing atomic numbers.Periodic Law: The phsical and chemical properties of the elements are the periodic functions of their atomic numbers.Glenn Seaborg(UC Berkeley, 1944)Formed Actinide Seriesjust like that of thelanthanides (#58-71)
5Basics of the Periodic Table periodic: a repeating patterntable: an organized collection of informationperiod: horizontal row on the P.T.Designates e- energy levelsgroup or family: vertical column on the P.T.Periodic Table: an arrangement of elements in order of atomic number; elements with similar properties appear at regular intervals (are in the same group)
6Electron Structures of Atoms nucleuse-e-1st energy levele-1st Period: Hydrogen (#1) Helium (#2)e-2nd energy levele-e-e-e-e-e-e-e-e-2nd Period: Lithium (#3) Neon (#10)
7S block elements: Group 1 & 2 Chemically reactive metals, group 1 more reactive than group 2. Group Config: ns 1-2Alkali metals:silvery appearance, soft enough to cut with a knife, not found in nature as free elements. H shares e-config but not properties.Alkaline-earth metals:harder, denser, stronger, and have a higher melting point than group 1. Too reactive to be found uncombined in nature. He shares e- config but not properties.
8p block elements: Group 13-18 Includes all the three types of elements: metals, non metals and metalloids.Group Config: ns2 np 1-6Includes Halogens: most reactive of the nonmetals. React vigorously with most metals to form salts.P block metals are generally harder & denser than s block but softer & less dense than d block metals.Found in nature solely as compounds except for bismuth.
9d block elements: Group 3-12 Transition Elements: metals with typical properties; good conductors, high luster.Less reactive than s block, many existing in nature as free elements.Electrons added to the d sublevel of the preceding energy level (n-1).Group configuration: (n-1)d1-10ns 0-2Some deviations from orderly d sublevel filling occur in group 4-11(s electrons jumping to d sublevel)
10f-block elementsF-block elements are wedged between groups 3 and 4 in the sixth and seventh period, consisting of lanthanides and actinidesMost elements are radioactiveTrans Uranium elements are all syntheticGroup Config: ns 0-2 (n-1) d 0-1 (n-2)f 1-14
11atomic radius:Covalent Radius for Covalently Bonded Atoms: half the distance between the nuclei of two covalently bonded atomsF-F bond length is 144 pm, so F covalent radius is 72 pm.H-F bond length is 109 pm, so H covalent radius is 37 nm.Atomic Radius for Elements like the Noble GasesAr atomic radius is 131 pmMetallic Radius for MetalsAl metallic radius is 143 pm.
126.3Trends in Atomic SizeThe atomic radius is one half of the distance between the nuclei of two atoms of the same element when the atoms are joined.This diagram lists the atomic radii of seven nonmetals. An atomic radius is half the distance between the nuclei of two atoms of the same element when the atoms are joined.
136.3Trends in Atomic SizeThis graph plots atomic radius versus atomic number for 55 elements. INTERPRETING GRAPHS a. Analyzing Data Which alkali metal has an atomic radius of 238 pm? b. Drawing Conclusions Based on the data for alkali metals and noble gases, how does atomic size change within a group? c. Predicting Is an atom of barium, atomic number 56, smaller or larger than an atom of cesium (Cs)?
146.3The size of atoms tends to decrease from left to right across a period and increase from top to bottom within a group. Predicting If a halogen and an alkali metal are in the same period, which one will have the larger radius?
15Cation=positive ion, Anion=negative ion Ionic RadiiForming a cation by losing electron(s) leads to a decrease in atomic radius, a smaller electron cloud.Forming an anion by electron(s) leads to an increase in atomic radius, less pull from the nucleus & there is more repulsion between the greater number of electrons.
166.3CationsWhen a sodium atom loses an electron, it becomes a positively charged ion. When a chlorine atom gains an electron, it becomes a negatively charged ion. Interpreting Diagrams What happens to the protons and neutrons during these changes?
176.3AnionsWhen a sodium atom loses an electron, it becomes a positively charged ion. When a chlorine atom gains an electron, it becomes a negatively charged ion. Interpreting Diagrams What happens to the protons and neutrons during these changes?
18Across a period atoms become smaller. Down a group atoms become larger.
19Ionization EnergyAmount of energy required to remove an e from a neutral atom in its gaseous state.First Ionization EnergyA(g) A+(g) + e-Second Ionization EnergyA+(g) A2+(g) + e-Third Ionization EnergyA2+(g) A3+(g) + e-
20Picture of IE trendI.E. increases across a period and decreases down a group.
21Trends in Ionization Energy 6.3Trends in Ionization Energy
22Trends in Ionization Energy 6.3Trends in Ionization EnergyFirst ionization energy tends to increase from left to right across a period and decrease from top to bottom within a group. Predicting Which element would have the larger first ionization energy—an alkali metal in period 2 or an alkali metal in period 4?
23Electron AffinityAmount of energy released when an e is added to a gaseous atom in its neutral state.First Electron AffinityA(g) + e- A-(g)Second Electron AffinityA-(g) + e- A2-(g)Third Electron AffinityA2-(g) + e- A3-(g)
24ElectronegativityA measure of the ability of an atom in a chemical compound to attract electrons.Fluorine, the most electronegative element, is arbitrarily assigned a value of 4.0. Values for other elements are calculated in relation to this.Tend to increase across a periodTend to decrease down a group or remain about the same.If an element does not form a compound, some noble gases, will not have a value.
25Trends in Electron Affinity and Electronegativity Both electron affinity and electronegativity increase from L to R across a period.Both electron affinity and electronegativity decrease down a group.
26Two Factors Used to Explain Trends The principal energy levelAll other factors being equal, increased n for the orbitals in which electrons are found means increased size of orbitals, which leads to decreased attraction for electrons from the nucleus.
27Effective Nuclear Charge Effective charge is the approximate net nuclear charge felt by the highest energy electrons.All other factors being equal, increased effective charge means increased attraction for electrons, which leads to decreased size of orbitals.Effective charge depends upon two factors:Total nuclear charge: # of protons (greater the total nuclear charge, higher the attraction felt by electrons)# of shielding electrons (e present in between the nucleus and the valence shell electrons, the higher the number of shielding electrons, the lesser is the effective nuclear charge)
28SHIELDING:The net nuclear charge felt by an outer electron is substantially lower than the actual nuclear charge. the outer electrons are shielded from the full charge of the nucleus by the inner electrons, which is called shielding effect.