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Periodic Groups & Trends

Explore the regular variations in properties with increasing atomic weight on the periodic table. Learn about the alkali metals, halogens, transition metals, noble gases, lanthanides, and actinides. Understand the trends in atomic radii, ionization energy, ionic radii, and electronegativity.

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Periodic Groups & Trends

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  1. Periodic Groups and Trends

  2. Periodic Table • Periodicity: regular variations (or patterns) of properties with increasing atomic weight. Both chemical and physical properties vary in a periodic (repeating pattern). • Group: vertical column of elements (“family”) • Period: horizontal row of elements

  3. Activity: get out your black and white copy of the periodic table.

  4. On one side, color and label the metals, nonmetals, and metalloids. Another name for “metalloid” is “semi-metal”.

  5. Color and label the groups/families of elements on the other side of your paper. Remember to create a legend. noble gases Transition metals alkali metals halogens alkaline earth metals lanthanides actinides

  6. PERIODIC GROUPS • alkali metals • alkaline earth metals • transition metals • halogens • noble gases • lanthanides • actinides

  7. Alkali Metals • Group 1 on periodic table • Very reactive • Soft solids • Readily combine with halogens (ex. NaCl) • Tendency to lose one electron (to become an ion)

  8. Alkaline Earth Metals • Group 2 on periodic table • Abundant metals in the earth • Not as reactive as alkali metals • Higher density and melting point than alkali metals

  9. Transition Metals • Groups 3-12 on periodic table Important for living organisms (think vitamins: multivitamins (they have iron, zinc, chromium, etc.)

  10. Halogens • Group 7A on periodic table (***or GROUP 17) • “Salt former” – combines with groups 1 and 2 to form salts (ionic bonds)

  11. Noble Gases • Group 8 on periodic table (** or GROUP 18) • Relatively inert, or nonreactive • Gases at room temperature

  12. Lanthanides • Part of the “inner transition metals” • Soft silvery metals • Tarnish readily in air • React slowly with water

  13. Actinides • Radioactive elements • Part of the “inner transition metals”

  14. PERIODIC TRENDS • Atomic radii • Ionization energy • Ionic radii • Electronegativity

  15. Atomic Radii

  16. Atomic Radii • Trend: increases down a group • WHY??? • The atomic radius gets bigger because electrons are added to energy levels farther away from the nucleus. • Plus, the inner electrons shield the outer electrons from the positive charge (“pull”) of the nucleus; known as the SHIELDING EFFECT

  17. Atomic Radii • Trend: decreases across a period • WHY??? • As the # of protons in the nucleus increases, the positive charge increases and as a result, the “pull” on the electrons increases.

  18. Ionization Energy • Definition: energy required to remove outer electrons

  19. Ionization Energy • Definition: energy required to remove outer electrons

  20. Ionization Energy • Trend: decreases down a group • WHY??? • Electrons are in higher energy levels as you move down a group; they are further away from the positive “pull” of the nucleus and therefore easier to remove.

  21. Ionization Energy • Trend: increases across a period • WHY??? • The increasing charge in the nucleus as you move across a period exerts greater “pull” on the electrons; it requires more energy to remove an electron.

  22. Ionic Radii • Cations are always smaller than the metal atoms from which they are formed. (fewer electrons because metals LOSE electrons) • Anions are always larger than the nonmetal atoms from which they are formed. (more electrons because nonmetals GAIN electrons)

  23. Electronegativity • Definition: the tendency of an atom to attract electrons to itself when chemically combined with another element

  24. Electronegativity • Trend: decreases down a group • WHY??? • Although the nuclear charge is increasing, the larger size produced by the added energy levels means the electrons are farther away from the nucleus; decreased attraction, so decreased electronegativity; plus, shielding effect

  25. Electronegativity • Trend: increases across a period (noble gases excluded!) • WHY??? • Nuclear charge is increasing, atomic radius is decreasing; attractive force that the nucleus can exert on another electron increases.

  26. Summing Up Periodic Trends

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