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Chapter 4

Chapter 4. Learning Objectives. Understand the development and need for the periodic table Identify the properties and locations of families on the periodic table Identify trends of atomic properties. Dmitri Mendeleev. 1869 63 known Elements Arranged by atomic mass. Henry Moseley.

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Chapter 4

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  1. Chapter 4

  2. Learning Objectives • Understand the development and need for the periodic table • Identify the properties and locations of families on the periodic table • Identify trends of atomic properties

  3. Dmitri Mendeleev 1869 63 known Elements Arranged by atomic mass

  4. Henry Moseley • 1913 • Organized elements by atomic number rather than atomic mass

  5. Modern Versions – all follow the periodic law Theorodore Benfrey - 1960 Timothy Stowe

  6. ADOMAH – good for electron config.

  7. Why do the properties of elements repeat themselves at regular intervals? Valence Electrons

  8. Groups Periods

  9. Main-Group Elements • Wide range of properties • Solids, liquids, gases • About half are metals • Many are very reactive, some are not reactive • Silicon and oxygen account for four of every five atoms found on or near Earth’s surface

  10. Group 1 – Alkali Metals • React with water to form alkaline solutions • One valence electron – very reactive • Not found in nature as pure elements • Metals are very soft, easily cut with a knife • Good conductors of electricity

  11. Group 2 – Alkaline-Earth Metals • Slightly less reactive than alkali metals • (still very reactive) • Two valence electrons • Harder than alkali metals, higher melting points • Last one in the family, Radium is radioactive

  12. Mg Hg Sr Metals • Excellent conductors of electricity • Conductors of heat • Some are ductile (can be drawn into a wire) • Some are malleable (can be hammered or rolled into sheets)

  13. Transition Metals • Group members do not have identical electron configurations • May lose different numbers of valence electrons during reactions • Less reactive than Group 1&2 • Gold, platinum, and palladium are the least reactive TMs • Good conductors of heat • Ductile and malleable

  14. NonMetals • C, N, O, P, S, Se • Not good conductors of heat or electricity • Brittle • No metallic luster • Most abundant elements on earth

  15. Metalloids • B, Si, Ge, As, Sb, Te, Po • Behave like nonmetals chemically and physically • Electrical conductivity like metals • Semiconductors – conduct electricity weakly

  16. Group 7 - Halogens • Most reactive group of non-metals • Seven valence electrons (one short of stable) • F2, Cl2 are gases at RT • Br2 is a liquid at RT • I2 and At2 are solids at RT

  17. Group 8 – Noble Gases • Also known as noble gases • Mostly unreactive • Full set of electrons in outer shell

  18. Lanthanides and Actinides • Fill “f” orbitals • Called Lanthanides because they follow Lanthanum on the periodic table • Actinides follow – Actinium • All actinides are radioactive (unstable nuclei) • Shiny metals • Similar in reactivity to alkaline-earth metals

  19. Atomic Radius • How do you measure the radius of an atom?

  20. Atomic Radius • One way - Bond Radius

  21. Atomic Radius Trends Why? Increasing energy levels Why? Increasing nuclear charge pulls electrons inward

  22. Ionization Energy • The energy required to remove an electron from an atom of an ion

  23. Ionization Energy Trends Why? Electron Shielding Father from nucleus Why? Increasing nuclear charge, harder to remove an electron

  24. Electron Affinity • The energy change that occurs when a neutral atom gains an electron Why? Electron Shielding Father from nucleus Why? Increasing nuclear charge, goal is to be complete

  25. Electronegativity • A measure of the ability of an atom in a compound to attract electrons Why? Electron Shielding Father from nucleus Why? Increasing nuclear charge, stronger (+) attraction

  26. Electronegativity • Why is the no color-coding for He, Ne, and Ar?

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