1 / 17

Section 3: Periodic Trends

Section 3: Periodic Trends. Nuclear Charge. Nuclear charge is the pull that an electron “feels” from the nucleus. The closer an electron is to the nucleus, the more pull it feels. As nuclear charge increases , the electron cloud is pulled in tighter . Increases across a period.

freidacarroll
Download Presentation

Section 3: Periodic Trends

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Section 3: Periodic Trends

  2. Nuclear Charge • Nuclear charge is the pull that an electron “feels” from the nucleus. • The closer an electron is to the nucleus, the more pull it feels. • As nuclear charge increases, the electron cloud is pulled in tighter. • Increases across a period.

  3. Shielding • As more energy levels are added to atoms, the inner layers of electrons shield the outer electrons from the nucleus. • Outer electrons are less tightly held. • Constant across a period. • Increases down a group.

  4. Atomic Radius • Definition: Half of the distance between nuclei in covalently bonded diatomic molecule

  5. Atomic Radius decreases across a period • -due to greaternuclear charge • (more protons) • -due to • more • shielding • (more energy levels) increases down a group

  6. Atomic Radius

  7. Example of Atomic Radius Trend • Arrange the following elements in order of increasing atomic radii: Cs, F, K, Cl

  8. Ionic Radius Cations from metals: • e–’s lost • positive (+) charge • smaller • outer shelllost • Anions from nonmetals: • e–’s gained • negative (–) charge • larger • less nuclear charge

  9. + + Ions • Here is a simple way to remember which is the cation and which the anion: This is Ann Ion. This is a cat-ion. She’s unhappy and negative. He’s a “plussy” cat!

  10. Cation Formation Nuclear charge on remaining electrons increases. Na atom 1 valence electron Remaining e- are pulled in closer to the nucleus. Ionic size decreases. 11p+ Valence e- lost in ion formation Result: a smaller sodium cation, Na+

  11. Anion Formation A chloride ion is produced. It is larger than the original atom. Chlorine atom with 7 valence e- 17p+ One e- is added to the outer shell. Nuclear charge is reduced and the e- cloud expands.

  12. Ionic Radius Notice that the anions are larger than the cations!

  13. Example of Ionic Radius Trend • Arrange the following ions in order of increasing ionic radii: Ca2+, K+, Al3+, S2-, Cl-, Te2-

  14. Quick Quiz! • Atoms get ___ down a group due to ___. • bigger, greater nuclear charge (protons) • smaller, less nuclear charge (protons) • bigger, more shielding (levels) • smaller, less shielding (levels)

  15. Quick Quiz. • Atomic radii ___ across a period due to ___. • decrease, greater nuclear charge (protons) • decrease, less nuclear charge (protons) • increase, more shielding (levels) • increase, less shielding (levels)

  16. WHY? Quick Quiz. most shielding (levels) least nuclear charge (protons) • Which of the following has the largest radius? • Na • Mg • K • Ca

  17. Quick Quiz. • Metals tend to ________ electrons to form _________ cations. • gain, positive • gain, negative • lose, negative • lose, positive

More Related