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Understanding Periodic Trends in Atomic Properties

Explore the concepts of atomic radii, ionization energy, electron affinity, ionic radii, and electronegativity in the periodic table. Learn how these properties change across periods and groups. Discover exceptions to these trends and the role of valence electrons. Helpful links provided for further engagement.

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Understanding Periodic Trends in Atomic Properties

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  1. Periodic Properties

  2. Valence Electrons • Valence electrons – Electrons in the outer energy level that can be lost, gained, or shared (connected to the group #)

  3. Atomic Radii • The atomic radius is a measure of the size of an atom (½ distance betw 2 nuclei). • The larger the radius, the larger is the atom. • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/atomic4.swf • http://www.youtube.com/watch?v=YS71PbwUPx8

  4. Atomic Radii

  5. Atomic Radii • Radii decrease across a period because the nucleus gets a larger positive charge • Radii increase down a group because the nucleus gets larger • Which is larger and why? Which is the smallest? Li, O, C, or F • Largest: Li Smallest: F • What about Be, Mg, Ca, or Sr? • Largest: Sr Smallest: Be

  6. Ionization Energy • Ion – an atom that has a positive or negative charge • Ionization – process that results in forming an ion • Ionization energy (IE) – energy required to remove one electron from a neutral atom (energy needed to make a positive charge)

  7. Ionization Energy A + Energy A+ + e- • IE increases across a period because the nuclear charge increases (more electrons in the orbitals) • IE decreases down a group because it is easier to remove e- from higher energy levels

  8. Electron Affinity • Electron Affinity (EA) – energy needed to add an electron to a neutral atom (opposite of IE). A + e- A- + energy

  9. Electron Affinity • EA decreases across periods (get more negative) • EA decreases down groups as nuclear charge increases. ***There are many exceptions to this rule!!!

  10. Ionic Radii • Cation – positive ion (decrease in atomic radii) • Anion – negative ion (increase in atomic radii) • Ionic radii decrease across periods because the electron cloud shrinks • Ionic radii increase down groups as energy levels increase

  11. Electronegativity • Electronegativity -- the ability of an atom to attract electrons • Electronegativities increase across a period and decrease down groups (but there are exceptions!) **Fluorine is the most electronegative atom!!

  12. The Best Way to Remember…. • Just know all the trends that surround Fluorine, and work your way down or across! • F – most electronegative, highest IE, lowest EA, small atomic and ionic radii

  13. All Periodic Trends

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