2Mendeleev and Chemical Periodicity Mendeleev noticed that when the elements were arranged in order of increasing atomic mass, certain similarities in their chemical properties appeared at regular intervals.Repeating patterns are referred to as periodic.Mendeleev created a table in which elements with similar properties were grouped together—a periodic table of the elements.
3Mendeleev’s Periodic Table Dmitri MendeleevRefer to pg 124Text – ForElements out ofPlace.Dmitri Mendeleev
4Properties of Some Elements Predicted By Mendeleev
5Moseley and the Periodic Law In 1911, the English scientist Henry Moseley discovered that the elements fit into patterns better when they were arranged according to atomic number, rather than atomic weight.The Periodic Law states that the physical and chemical properties of the elements are periodic functions of their atomic numbers.What does this mean?
7Lanthanides – Atomic # 58-71 added to the periodic table in 1900. Noble Gases – Group 18 or VIII – Unreactive gases with eight valence electrons.Lanthanides – Atomic # added to the periodic table in 1900.Actinides – Atomic #Noble Gases – Group 18 or VIII – Unreactive gases with eight valence electrons. This group was added to the periodic table when Strutt and Ramsay discovered Argon and then subsequently Ramsay discovered Kr and Xe. Radon was discovered in 1900 by Dorn.
8The Modern Periodic Table The Periodic Table is an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group.Period or series - A horizontal row across the periodic table (7 total)Group or family – A vertical column on the periodic table (18 total)
10PeriodThe Periodic TableGroup or FamilyGroup or familyPeriod
11The Properties of Group I: the Alkali Metals Never found pure in natureEasily lose valence electron React violently with water In their pure states,they have asoft silvery appearance and canbe cut with a knife React with halogens to form saltsGroup configuration = ns1n arrangement of the elements in
12Group 2 of the periodic table alkaline-earth metals.beryllium, magnesium, calcium, strontium, barium, and radiumGroup 2 metals are less reactive than the alkali metals, but are still too reactive to be found in nature in pure form.Group configuration ns2Radium was widely used in self-luminous clock and watch hands, until too many watch factory workers had died of it. This antique watch is still quite radioactive and will remain for thousands of years.
13Halogens – Group 17 or VIIReact vigorously with most metals to form salts.Fluorine and chlorine are gases at room temp., bromine is a reddish liquid, and iodine is a dark purple solid.Astantine is a synthetic element prepared in very small quantities.Group configuration ns2np5Halogens – Group 17 or VII
14Transition Metals “Group B Metals” Many exceptions to Aufbau exist in this area. Why? Why was the mad hatter mad?
15Properties of MetalsMetals are good conductors of heat and electricityMetals are malleableMetals are ductileMetals have high tensile strengthMetals have lusterLocated to the left ofthe zigzag line on theperiodic table
16Examples of MetalsPotassium, K reacts with water and must be stored in keroseneCopper, Cu, is a relatively soft metal, and a very good electrical conductor.Zinc, Zn, is more stable than potassiumMercury, Hg, is the only metal that exists as a liquid at room temperature
17Properties of Nonmetals Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element.Nonmetals are poor conductors of heat andelectricityNonmetals tend to be brittleMany nonmetals are gases at room temperatureLocated to the right of the zigzag line on the periodic table
18Examples of NonmetalsMicrospheres of phosphorus, P, a reactive nonmetalSulfur, S, was once known as “brimstone”Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure
19Properties of Metalloids Metalloids straddle the border between metals and nonmetals on the periodic table.They have properties of both metals and nonmetals.Metalloids are more brittle than metals, less brittle than most nonmetallic solidsMetalloids are semiconductors of electricitySome metalloids possess metallic luster
20Silicon, Si – A Metalloid Silicon has metallic lusterSilicon is brittle like a nonmetalSilicon is a semiconductor of electricityOther metalloids include:Boron, BGermanium, GeArsenic, AsAntimony, SbTellurium, Te
21Blocks of the Periodic Table d bdlocks blockfThe s and p blocks = the main group elements.The d block = the transition metals.The f block = the inner transition metals.f blockThe s and p blocks = the main group elements.The d block = the transition metals.The f block = the inner transition metals.
22Periods and Blocks of the Periodic Table Sample Problem Aa. Without looking at the periodic table, identify the group, period, and block in which the element that has the electron configuration [Xe]6s2 is located.b. Without looking at the periodic table, write the electron configuration for the Group 1 element in the third period. Is this element likely to be more reactive or less reactive than the element described in (a)?
23Solution for Sample Problem A It is in the sixth period, as indicated by the highest principal quantum number in its configuration, 6.The element is in the s block. The element is in Group 2, as indicated by the group configuration of ns2.Solution for Sample Problem A
24Sample Problem BAn element has the electron configuration [Kr]4d55s1. Without looking at the periodic table, identify the period, block, and group in which this element is located. Then, consult the periodic table to identify this element and the others in its group.
25Sample Problem B Solution The number of the highest occupied energy level is 5, so the element is in the fifth period.There are five electrons in the d sublevel, which means that it is incompletely filled. The d sublevel can hold 10 electrons. Therefore, the element is in the d block.For d-block elements, the number of electrons in the ns sublevel (1) plus the number of electrons in the (n 1)d sublevel (5) equals the group number, 6. This Group 6 element is molybdenum.
26Sample Problem CWithout looking at the periodic table, write the outer electron configuration for the Group 14 element in the second period. Then, name the element, and identify it as a metal, nonmetal, or metalloid.
27Sample Problem C Solution The group number is higher than 12, so the element is in the p block.The total number of electrons in the highest occupied s and p sublevels is therefore equal to the group number minus 10 (14 10 = 4).Two electrons are in the s sublevel, so two electrons must also be present in the 2p sublevel.The outer electron configuration is 2s22p2.The element is carbon, C, which is a nonmetal.
28Sample Problem DName the block and group in which each of the following elements is located in the periodic table. Then, use the periodic table to name each element. Identify each element as a metal, nonmetal, or metalloid. Finally, describe whether each element has high reactivity or low reactivity.a. [Xe]4f145d96s1 c. [Ne]3s23p6b. [Ne]3s23p d. [Xe]4f66s2
29Sample Problem D Solution a.The 4f sublevel is filled with 14 electrons. The 5d sublevel is partially filled with nine electrons. Therefore, this element is in the d block.The element is the transition metal platinum, Pt, which is in Group 10 and has a low reactivity.b. The incompletely filled p sublevel shows that this element is in the p block.A total of seven electrons are in the ns and np sublevels, so this element is in Group 17, the halogens.The element is chlorine, Cl, and is highly reactive.
30Sample Problem D Solution c. This element has a noble-gas configuration and thus is in Group 18 in the p block.The element is argon, Ar, which is an unreactive nonmetal and a noble gas.d. The incomplete 4f sublevel shows that the element is in the f block and is a lanthanide.Group numbers are not assigned to the f block.The element is samarium, Sm. All of the lanthanides are reactive metals.Sample Problem D Solution
33Determination of Atomic Radius Periodic Trends in Atomic Radius Half of the distance between nuclei in covalently bonded diatomic molecule "covalent atomic radii”Periodic Trends in Atomic RadiusRadius decreases across a periodIncreased effective nuclear charge dueto decreased shieldingRadius increases down a groupAddition of principal quantum levels
35Lithium configuration Lithium ion configurationCompare two cations
36Oxygen ion configuration Oxygen configurationOxygen ion configurationCompare two anions
37Increases for successive electrons taken from the same atom Ionization Energy - the energy required to remove an electron from an atomIncreases for successive electrons taken fromthe same atomTends to increase across a periodElectrons in the same quantum level donot shield as effectively as electrons ininner levels Irregularities at half filled and filledsublevels due to extra repulsion ofelectrons paired in orbitals, making themeasier to removeTends to decrease down a groupOuter electrons are farther from thenucleus
39Most atoms release energy when they acquire an electron Electron Affinity - The energy change that occurs when an electron is acquired by a neutral atom.Most atoms release energy when they acquire an electronElectron Affinity - The energy change that occurs when an electron is acquired by a neutral atom.Most atoms release energy when they acquire an electronA + e- → A - + energy
40Electronegativity A measure of the ability of an atom in a chemical compound to attract electronsElectronegativities tend to increaseacross a periodElectronegativities tend to decreasedown a group or remain the same
42Ionic Radii Cations Anions Positively charged ions formed when an atom of a metal loses one ormore electronsCations Smaller than the correspondingatomNegatively charged ions formedwhen nonmetallic atoms gain oneor more electronsAnionsLarger than the correspondingatom