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Periodic Table and Electrons

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Periodic Table and Electrons Chemistry Learning Objectives Atomic Theory and Periodic Table Essential knowledge and skills: Distinguish between a group and a period. Identify key groups, periods, and regions of elements on the periodic table. Identify and explain trends in the periodic table as they relate to ionization energy, electronegativity, shielding effect, and relative sizes. Compare an element’s reactivity to the reactivity of other elements in the table. Relate the position of an element on the periodic table to its electron configuration. Determine the number of valence electrons and possible oxidation numbers from an element’s electron configuration. Write the electron configuration for the first 20 elements of the periodic table. Essential understandings: The periodic table is arranged in order of increasing atomic numbers. The names of groups and periods on the periodic chart are alkali metals, alkaline earth metals, transition metals, halogens, and noble gases. Metalloids have properties of metals and nonmetals. They are located between metals and nonmetals on the periodic table. Some are used in semiconductors. Periods and groups are named by numbering columns and rows. Horizontal rows called periods have predictable properties based on an increasing number of electrons in the outer energy levels. Vertical columns called groups or families have similar properties because of their similar valence electron configurations. The Periodic Law states that when elements are arranged in order of increasing atomic numbers, their physical and chemical properties show a periodic pattern. Periodicity is regularly repeating patterns or trends in the chemical and physical properties of the elements arranged in the periodic table. Atomic radius is the measure of the distance between radii of two identical atoms of an element. Atomic radius decreases from left to right and increases from top to bottom within given groups. Electronegativity is the measure of the attraction of an atom for electrons in a bond. Electronegativity increases from left to right within a period and decreases from top to bottom within a group. Shielding effect is constant within a given period and increases within given groups from top to bottom. Ionization energy is the energy required to remove the most loosely held electron from a neutral atom. Ionization energies generally increase from left to right and decrease from top to bottom of a given group. Electron configuration is the arrangement of electrons around the nucleus of an atom based on their energy level. Electrons are added one at a time to the lowest energy levels first (Aufbau Principle). Electrons occupy equal-energy orbitals so that a maximum number of unpaired electrons results (Hund’s Rule). Energy levels are designated 1–7. Orbitals are designated s, p, d, and f according to their shapes and relate to the regions of the Periodic Table. An orbital can hold a maximum of two electrons (Pauli Exclusion Principle). Atoms can gain, lose, or share electrons within the outer energy level. Loss of electrons from neutral atoms results in the formation of an ion with a positive charge (cation). Gain of electrons by a neutral atom results in the formation of an ion with a negative charge (anion). ELEMENTS AND THE PERIODIC TABLE WHAT’S IN THE NAME? Provide the name and chemical symbol for the element, which sounds similar to a possible correct answer. See number one for an example. CLUE ELEMENT CLUE ELEMENT 1. well drillers decision boron B 24. a spice 2. to press laundry 25. a blitz by police 3. policeman 26. …..on the Range 4. mother’s sister’s money 27. …of Arabia 5. where dishes are washed 28. dull chemistry lecture 6. a foolish prisoner 29. Golden Gate Bridge state 7. natives of North America 30. …bladder or …stones 8. water and gin 31. European country 9. shown the way 32. another European country 9 10. I sit down to eat 33. repair clothes 11. a Ford product 34. 50 per cent 12. a popular house plant 35. larger than a coyote 13. have the sniffles 36. God of the underworld 14. United States citizen 37. God of the sea 15. don’t take any wooden 38. a good . (helper) 16. playing a part or role 39. to brown a roast 17. pop 40. girl’s names calcium Ca 18. a lisper saying “listening” (many options!) 19. technician 20. Lone Ranger’s horse 21. endure or tolerate pain 22. what you walk on at home 23. leg joint above calf CLUE: ium ending read as “him” ELEMENT 1. doctors do this helium (heel him) 2. doctors do this too 3. funeral homes do this 4. cowboys do this to horses 5. “Anything to keep him quiet” mother says to father. 6. grab him 7. to get him off my back History of the Periodic Table J.A.R. Newlands - 1867 first version of Periodic Table. Newlands arranged the known elements by increasing atomic mass along horizontal rows seven elements long, stated that the 8th element would have similar properties to the first from the series. Newlands called this the law of octaves. Newlands' work failed after Ca in predicting a consistent trend. Dimitri Mendeleev 1869, Professor of Chemistry at the University of Saint Petersburg (Leningrad). Mendeleev stated that the elements vary periodically (in cycles) according to their atomic masses. Mendeleev separated his elements and left spaces on his table in order for the periodicity to continue. He then predicted that elements would be discovered to fill these "gaps" in the table. Mendeleev even accurately stated the properties of these elements. Scandium (eka-boron), gallium (eka-aluminum), and germanium (eka-silicon). By 1886 all of the elements predicted by Mendeleev had been isolated. When Mendeleev's notes show that the periodic system was created in a single day, February 17, 1869. He arrived at his system by puzzling over cards containing the names of the 63 known elements along with their atomic weights and important chemical and physical properties. Lothar Meyer-1886, also developed a periodic table based on atomic masses, independently of Mendeleev. Meyer had several inaccuracies and some elements were not included. Meyer was the first scientist to introduce the concept of valence as a periodic property. Both Mendeleev and Meyer were awarded the Royal Societies Davy Medal. Mendeleev is given credit because of his accurate property prediction of yet undiscovered elements. 10 Henry Moseley-1914 was a student of Rutherford. Moseley was studying X-ray formation by high energy electron bombardment. He graphed the square root of the X-ray frequency vs atomic mass. This plot gave a nearly linear line except for three atomic pairs. Ar(39.95)/K(39.10), Co(58.93)/Ni(58.69), Te(127.60)/I(126.90). When the atoms were plotted according to atomic number, then a linear relationship was established. Moseley stated, "There is every reason to suppose that the integer that controls the X-ray spectrum is the charge on the nucleus." Periodic Law - The properties of the chemical elements are a periodic function of atomic number. Why Mendeleev is given Credit in Modern Text Books? Mendeleev's Table allowed for and was capable of adjusting to future discoveries: noble gases, new column in 1894-1901 incorporation of the rare earth elements Moseley's atomic number in 1914 Bohr atom and electronic structure in 1913 discovery of synthetic elements 1939 to present (element 110, 1994) The Periodic Table Group a vertical column of elements in the periodic table; also called a family Period a horizontal row of elements in the periodic table Metals one of a class of elements that includes a large majority of the known elements; metals are characteristically lustrous, malleable, ductile, and good conductors of heat and electricity Metalloids The elements that border the stair-stepped line are classified as metalloids. The metalloids, or semimetals, have properties that are somewhat of a cross between metals and nonmetals. Metalloids tend to be economically important because of their unique conductivity properties (they only partially conduct electricity), which make them valuable in the semiconductor and computer chip industry. The metalloids are shown in the following illustration. Nonmetals one of a class of elements that are not lustrous and are generally poor conductors of heat and electricity; nonmetals are grouped on the right side of the periodic table 11 Alkali metals any metal in Group 1 of the periodic table. (soft, malleable, lustrous, good conductors, MOST REACTIVE family of metals) Alkaline earth metals any metal in Group 2 of the periodic table. (higher densities and melting points than alkali metals; not as reactive as alkali) Halogens any member of the nonmetallic elements in Group 17 in the periodic table. ( MOST REACTIVE Non-Metals; do not occur free in nature; commonly found in sea water, minerals, & living tissues) Noble gases any member of a group of gaseous elements in Group 18 in the periodic table. (VERY INACTIVE elements, used in balloons, scuba diving tanks, light bulbs) Periodic Table Exercise The following need to be labeled on your periodic table metals/non-metals jewellery metals (there are three of them) magnetic metals (three of them) elements that are gases at room temperature the two liquid elements at room temperature noble gases alkali earth elements halogens alkali metals metalloids (seven of them) 12 Modern Atomic Theory Notes 1850's Robert Bunsen conducted experiments in which he observed that different elements, when heated in a flame, gave off a characteristic colour. Late 1800's J.J. Thomson and others were experimenting with gas discharge tubes. Gaseous elements, when subjected to electric current at low pressure, gave off a colourful glow. 1869 Dmitri Mendeleev introduced the scientific world to the idea of periodicity and that patterns of behavior within the elements were in accord with their atomic mass.
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