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Periodic Trends: Investigation and Understanding of the Atom in Chemistry

Explore the periodic trends in the properties of elements, such as atomic radii, ionization energy, electronegativity, and ionic radii. Learn about the history of the periodic table and the organization of elements into groups and periods.

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Periodic Trends: Investigation and Understanding of the Atom in Chemistry

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  1. Chapter 5:Periodic Trends The investigation and understanding of the atom is what chemistry is all about! Topics rearranged from your text. Over the next week, you should read pages 73-134 Periodic Law: …

  2. The Periodic Table • The Periodic Table • a collection of all the known elements into a model that groups elements with similar properties. • Groups • Vertical columns of elements with similar properties. • Periods • Horizontal rows of elements with atomic mass and similar electron configurations.

  3. Periodic Table History c 1869 • Dmitri Mendeleev • Russian chemist, ordered the known elements according to properties. (Gaps?) • Henry Moseley • arranged the elements according to atomic number(# of protons). • This is the system we use today. • Periodic Law • chemical and physical properties of elements are periodic functions of their atomic numbers. • The elements in the periodic table are arranged according to Periodic Law • Periodic Law shows certain trends in the properties of elements … c 1911

  4. Periodic Trends –Atomic Radii • As electrons are added to the outside of atoms, in the same period, the atom’s radius decreases. Why? • As new shells are added, radius increases. Text Page 141 Smaller from left to right

  5. Periodic Trends –Ionization Energy • Ionization Energy - the energy required to strip an electron from an atom. • As more electrons are added to a shell, it’s more difficult to remove them. (More protons pulling inward) • Easier to remove electrons from larger atoms. Text Page 143 Larger from left to right

  6. Period Trends –Electronegativity • Electronegativity (electron affinity) • an atom’s ability to attract electrons • Negative electron affinity = atom wants e-. • Decreases down a group Text Page 147 Larger from left to right

  7. Ionic Radii • +-attraction determines the atom’s radius. • An electron is added to a nonmetal atom : • Anion is formed. • Anions are larger than their neutral atom • An electrons is removed from a metal atom: • Cation is formed. • Cations are smaller than their neutral atoms e- Cl Cl- Why? Why? e- Na Na+

  8. Groups and their Properties • Recall: • elements in the same group have similar properties due to similar electron configurations. • Learn the following group-families and their basic chemical and physical properties: • Alkali Metals • Alkaline-Earth Metals • Transition Metals • Main-Block Elements • Noble Gasses • Rare-Earth Elements

  9. Group 1 (+1)Alkali Metals (s) • soft, highly reactive metals. • Lustrous • will reflect light, but these elements quickly lose their sheen when exposed to the air. • Electrically Conductive • able to pass a charge through the material. • often found in lights, batteries, and electrolytes. • Low melting points • Low density.

  10. Group 2 (+2)Alkaline-Earth Metals (s) • Properties are similar to group 1 elements, but are: • Harder • Less reactive than Group 1 elements. • (These elements are still very reactive.) • Lustrous • Electrically Conductive • Higher melting points than Group 1 metals. • More dense than Group 1 metals.

  11. Groups 3-12 (various)Transition Metals (d) • This is where we find most metals, including the coinage metals. • Lustrous • Electrically Conductive • Malleable • able to be shaped and formed, and hold that shape. • Ductile • able to be drawn into wires • Very hard • Verydense • High melting points

  12. Group 13-17 (+3-1)Main-Block Elements (p) • The most varied elements. • Liquids, gasses, and solids can be found in this group. Have widely varied properties • Includes Metalloids • elements having properties of both metals and non metals. • Most elements necessary to living things are found in this section. • Includes Halogens • Group 17 gasses and liquids F, Cl, Br, I, At • are very reactive due to very high electron affinities.

  13. Group 18 (0)Noble Gases (p) • Mostly unreactive. • All have filled octets. • Near zero electron affinity • Very high ionization energies. • Noble gasses make up a trace amount of our atmosphere • are mined from pockets of gases in the oceans. • When electrically charged: • noble gases produce brilliant plasmas, often used in signs.

  14. f – Group (various)Rare earth metals (f) • Very heavy, dense (large nuclei) • Most are radioactive. • Lanthanides • The first row, starting with lanthanum (57La) • (4f elements) • Actinides • The second row, starting with actinium (89Ac) • (5f elements) • Transuranium elements • All elements after Uranium92U(93Np on) are artificial. End of Chapter 5

  15. CCSD Syllabus Objectives • 6.1: Groups and Families • 6.2: Periodic Law • 6.3: Periodic Properties-Atomic Structure • 6.4: Periodic Properties-Periodic Law • 6.5: Groups and Trends • 6.6: Metals, Nonmetals, Metalloids • 6.7: Trends-atomic structures • 6.8: Electron config-p-table location • 7.4: Oxidation numbers

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